While with SLUB we can actually preassign tags for caches with contructors
and store them in pointers in the freelist, SLAB doesn't allow that since
the freelist is stored as an array of indexes, so there are no pointers to
store the tags.

Instead we compute the tag twice, once when a slab is created before
calling the constructor and then again each time when an object is
allocated with kmalloc.  Tag is computed simply by taking the lowest byte
of the index that corresponds to the object.  However in kasan_kmalloc we
only have access to the objects pointer, so we need a way to find out
which index this object corresponds to.

This patch moves obj_to_index from slab.c to include/linux/slab_def.h to
be reused by KASAN.

Link: http://lkml.kernel.org/r/c02cd9e574cfd93858e43ac94b05e38f891fef64.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Acked-by: NChristoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This commit adds rountines, that print tag-based KASAN error reports.
Those are quite similar to generic KASAN, the difference is:

1. The way tag-based KASAN finds the first bad shadow cell (with a
   mismatching tag). Tag-based KASAN compares memory tags from the shadow
   memory to the pointer tag.

2. Tag-based KASAN reports all bugs with the "KASAN: invalid-access"
   header.

Also simplify generic KASAN find_first_bad_addr.

Link: http://lkml.kernel.org/r/aee6897b1bd077732a315fd84c6b4f234dbfdfcb.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Move generic KASAN specific error reporting routines to generic_report.c
without any functional changes, leaving common error reporting code in
report.c to be later reused by tag-based KASAN.

Link: http://lkml.kernel.org/r/ba48c32f8e5aefedee78998ccff0413bee9e0f5b.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The krealloc function checks where the same buffer was reused or a new one
allocated by comparing kernel pointers.  Tag-based KASAN changes memory
tag on the krealloc'ed chunk of memory and therefore also changes the
pointer tag of the returned pointer.  Therefore we need to perform
comparison on untagged (with tags reset) pointers to check whether it's
the same memory region or not.

Link: http://lkml.kernel.org/r/14f6190d7846186a3506cd66d82446646fe65090.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Tag-based KASAN uses the Top Byte Ignore feature of arm64 CPUs to store a
pointer tag in the top byte of each pointer.  This commit enables the
TCR_TBI1 bit, which enables Top Byte Ignore for the kernel, when tag-based
KASAN is used.

Link: http://lkml.kernel.org/r/f51eca084c8cdb2f3a55195fe342dc8953b7aead.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Right now arm64 fault handling code removes pointer tags from addresses
covered by TTBR0 in faults taken from both EL0 and EL1, but doesn't do
that for pointers covered by TTBR1.

This patch adds two helper functions is_ttbr0_addr() and is_ttbr1_addr(),
where the latter one accounts for the fact that TTBR1 pointers might be
tagged when tag-based KASAN is in use, and uses these helper functions to
perform pointer checks in arch/arm64/mm/fault.c.

Link: http://lkml.kernel.org/r/3f349b0e9e48b5df3298a6b4ae0634332274494a.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Suggested-by: NMark Rutland <mark.rutland@arm.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

An object constructor can initialize pointers within this objects based on
the address of the object.  Since the object address might be tagged, we
need to assign a tag before calling constructor.

The implemented approach is to assign tags to objects with constructors
when a slab is allocated and call constructors once as usual.  The
downside is that such object would always have the same tag when it is
reallocated, so we won't catch use-after-frees on it.

Also pressign tags for objects from SLAB_TYPESAFE_BY_RCU caches, since
they can be validy accessed after having been freed.

Link: http://lkml.kernel.org/r/f158a8a74a031d66f0a9398a5b0ed453c37ba09a.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

virt_addr_is_linear (which is used by virt_addr_valid) assumes that the
top byte of the address is 0xff, which isn't always the case with
tag-based KASAN.

This patch resets the tag in this macro.

Link: http://lkml.kernel.org/r/df73a37dd5ed37f4deaf77bc718e9f2e590e69b1.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This commit adds a few helper functions, that are meant to be used to work
with tags embedded in the top byte of kernel pointers: to set, to get or
to reset the top byte.

Link: http://lkml.kernel.org/r/f6c6437bb8e143bc44f42c3c259c62e734be7935.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Move the untagged_addr() macro from arch/arm64/include/asm/uaccess.h
to arch/arm64/include/asm/memory.h to be later reused by KASAN.

Also make the untagged_addr() macro accept all kinds of address types
(void *, unsigned long, etc.). This allows not to specify type casts in
each place where the macro is used. This is done by using __typeof__.

Link: http://lkml.kernel.org/r/2e9ef8d2ed594106eca514b268365b5419113f6a.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Acked-by: NMark Rutland <mark.rutland@arm.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

A tag-based KASAN shadow memory cell contains a memory tag, that
corresponds to the tag in the top byte of the pointer, that points to that
memory.  The native top byte value of kernel pointers is 0xff, so with
tag-based KASAN we need to initialize shadow memory to 0xff.

[cai@lca.pw: arm64: skip kmemleak for KASAN again\
  Link: http://lkml.kernel.org/r/20181226020550.63712-1-cai@lca.pw
Link: http://lkml.kernel.org/r/5cc1b789aad7c99cf4f3ec5b328b147ad53edb40.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

With tag based KASAN mode the early shadow value is 0xff and not 0x00, so
this patch renames kasan_zero_(page|pte|pmd|pud|p4d) to
kasan_early_shadow_(page|pte|pmd|pud|p4d) to avoid confusion.

Link: http://lkml.kernel.org/r/3fed313280ebf4f88645f5b89ccbc066d320e177.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Suggested-by: NMark Rutland <mark.rutland@arm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Tag-based KASAN uses 1 shadow byte for 16 bytes of kernel memory, so it
requires 1/16th of the kernel virtual address space for the shadow memory.

This commit sets KASAN_SHADOW_SCALE_SHIFT to 4 when the tag-based KASAN
mode is enabled.

Link: http://lkml.kernel.org/r/308b6bd49f756bb5e533be93c6f085ba99b30339.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

This commit splits the current CONFIG_KASAN config option into two:
1. CONFIG_KASAN_GENERIC, that enables the generic KASAN mode (the one
   that exists now);
2. CONFIG_KASAN_SW_TAGS, that enables the software tag-based KASAN mode.

The name CONFIG_KASAN_SW_TAGS is chosen as in the future we will have
another hardware tag-based KASAN mode, that will rely on hardware memory
tagging support in arm64.

With CONFIG_KASAN_SW_TAGS enabled, compiler options are changed to
instrument kernel files with -fsantize=kernel-hwaddress (except the ones
for which KASAN_SANITIZE := n is set).

Both CONFIG_KASAN_GENERIC and CONFIG_KASAN_SW_TAGS support both
CONFIG_KASAN_INLINE and CONFIG_KASAN_OUTLINE instrumentation modes.

This commit also adds empty placeholder (for now) implementation of
tag-based KASAN specific hooks inserted by the compiler and adjusts
common hooks implementation.

While this commit adds the CONFIG_KASAN_SW_TAGS config option, this option
is not selectable, as it depends on HAVE_ARCH_KASAN_SW_TAGS, which we will
enable once all the infrastracture code has been added.

Link: http://lkml.kernel.org/r/b2550106eb8a68b10fefbabce820910b115aa853.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

We now have two KASAN modes: generic KASAN and tag-based KASAN.  Rename
kasan.c to generic.c to reflect that.  Also rename kasan_init.c to init.c
as it contains initialization code for both KASAN modes.

Link: http://lkml.kernel.org/r/88c6fd2a883e459e6242030497230e5fb0d44d44.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Tag-based KASAN reuses a significant part of the generic KASAN code, so
move the common parts to common.c without any functional changes.

Link: http://lkml.kernel.org/r/114064d002356e03bb8cc91f7835e20dc61b51d9.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The previous patch updated KASAN hooks signatures and their usage in SLAB
and SLUB code, except for the early_kmem_cache_node_alloc function.  This
patch handles that function separately, as it requires to reorder some of
the initialization code to correctly propagate a tagged pointer in case a
tag is assigned by kasan_kmalloc.

Link: http://lkml.kernel.org/r/fc8d0fdcf733a7a52e8d0daaa650f4736a57de8c.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Patch series "kasan: add software tag-based mode for arm64", v13.

This patchset adds a new software tag-based mode to KASAN [1].  (Initially
this mode was called KHWASAN, but it got renamed, see the naming rationale
at the end of this section).

The plan is to implement HWASan [2] for the kernel with the incentive,
that it's going to have comparable to KASAN performance, but in the same
time consume much less memory, trading that off for somewhat imprecise bug
detection and being supported only for arm64.

The underlying ideas of the approach used by software tag-based KASAN are:

1. By using the Top Byte Ignore (TBI) arm64 CPU feature, we can store
   pointer tags in the top byte of each kernel pointer.

2. Using shadow memory, we can store memory tags for each chunk of kernel
   memory.

3. On each memory allocation, we can generate a random tag, embed it into
   the returned pointer and set the memory tags that correspond to this
   chunk of memory to the same value.

4. By using compiler instrumentation, before each memory access we can add
   a check that the pointer tag matches the tag of the memory that is being
   accessed.

5. On a tag mismatch we report an error.

With this patchset the existing KASAN mode gets renamed to generic KASAN,
with the word "generic" meaning that the implementation can be supported
by any architecture as it is purely software.

The new mode this patchset adds is called software tag-based KASAN.  The
word "tag-based" refers to the fact that this mode uses tags embedded into
the top byte of kernel pointers and the TBI arm64 CPU feature that allows
to dereference such pointers.  The word "software" here means that shadow
memory manipulation and tag checking on pointer dereference is done in
software.  As it is the only tag-based implementation right now, "software
tag-based" KASAN is sometimes referred to as simply "tag-based" in this
patchset.

A potential expansion of this mode is a hardware tag-based mode, which
would use hardware memory tagging support (announced by Arm [3]) instead
of compiler instrumentation and manual shadow memory manipulation.

Same as generic KASAN, software tag-based KASAN is strictly a debugging
feature.

[1] https://www.kernel.org/doc/html/latest/dev-tools/kasan.html

[2] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html

[3] https://community.arm.com/processors/b/blog/posts/arm-a-profile-architecture-2018-developments-armv85a

====== Rationale

On mobile devices generic KASAN's memory usage is significant problem.
One of the main reasons to have tag-based KASAN is to be able to perform a
similar set of checks as the generic one does, but with lower memory
requirements.

Comment from Vishwath Mohan <vishwath@google.com>:

I don't have data on-hand, but anecdotally both ASAN and KASAN have proven
problematic to enable for environments that don't tolerate the increased
memory pressure well.  This includes

(a) Low-memory form factors - Wear, TV, Things, lower-tier phones like Go,
(c) Connected components like Pixel's visual core [1].

These are both places I'd love to have a low(er) memory footprint option at
my disposal.

Comment from Evgenii Stepanov <eugenis@google.com>:

Looking at a live Android device under load, slab (according to
/proc/meminfo) + kernel stack take 8-10% available RAM (~350MB).  KASAN's
overhead of 2x - 3x on top of it is not insignificant.

Not having this overhead enables near-production use - ex.  running
KASAN/KHWASAN kernel on a personal, daily-use device to catch bugs that do
not reproduce in test configuration.  These are the ones that often cost
the most engineering time to track down.

CPU overhead is bad, but generally tolerable.  RAM is critical, in our
experience.  Once it gets low enough, OOM-killer makes your life
miserable.

[1] https://www.blog.google/products/pixel/pixel-visual-core-image-processing-and-machine-learning-pixel-2/

====== Technical details

Software tag-based KASAN mode is implemented in a very similar way to the
generic one. This patchset essentially does the following:

1. TCR_TBI1 is set to enable Top Byte Ignore.

2. Shadow memory is used (with a different scale, 1:16, so each shadow
   byte corresponds to 16 bytes of kernel memory) to store memory tags.

3. All slab objects are aligned to shadow scale, which is 16 bytes.

4. All pointers returned from the slab allocator are tagged with a random
   tag and the corresponding shadow memory is poisoned with the same value.

5. Compiler instrumentation is used to insert tag checks. Either by
   calling callbacks or by inlining them (CONFIG_KASAN_OUTLINE and
   CONFIG_KASAN_INLINE flags are reused).

6. When a tag mismatch is detected in callback instrumentation mode
   KASAN simply prints a bug report. In case of inline instrumentation,
   clang inserts a brk instruction, and KASAN has it's own brk handler,
   which reports the bug.

7. The memory in between slab objects is marked with a reserved tag, and
   acts as a redzone.

8. When a slab object is freed it's marked with a reserved tag.

Bug detection is imprecise for two reasons:

1. We won't catch some small out-of-bounds accesses, that fall into the
   same shadow cell, as the last byte of a slab object.

2. We only have 1 byte to store tags, which means we have a 1/256
   probability of a tag match for an incorrect access (actually even
   slightly less due to reserved tag values).

Despite that there's a particular type of bugs that tag-based KASAN can
detect compared to generic KASAN: use-after-free after the object has been
allocated by someone else.

====== Testing

Some kernel developers voiced a concern that changing the top byte of
kernel pointers may lead to subtle bugs that are difficult to discover.
To address this concern deliberate testing has been performed.

It doesn't seem feasible to do some kind of static checking to find
potential issues with pointer tagging, so a dynamic approach was taken.
All pointer comparisons/subtractions have been instrumented in an LLVM
compiler pass and a kernel module that would print a bug report whenever
two pointers with different tags are being compared/subtracted (ignoring
comparisons with NULL pointers and with pointers obtained by casting an
error code to a pointer type) has been used.  Then the kernel has been
booted in QEMU and on an Odroid C2 board and syzkaller has been run.

This yielded the following results.

The two places that look interesting are:

is_vmalloc_addr in include/linux/mm.h
is_kernel_rodata in mm/util.c

Here we compare a pointer with some fixed untagged values to make sure
that the pointer lies in a particular part of the kernel address space.
Since tag-based KASAN doesn't add tags to pointers that belong to rodata
or vmalloc regions, this should work as is.  To make sure debug checks to
those two functions that check that the result doesn't change whether we
operate on pointers with or without untagging has been added.

A few other cases that don't look that interesting:

Comparing pointers to achieve unique sorting order of pointee objects
(e.g. sorting locks addresses before performing a double lock):

tty_ldisc_lock_pair_timeout in drivers/tty/tty_ldisc.c
pipe_double_lock in fs/pipe.c
unix_state_double_lock in net/unix/af_unix.c
lock_two_nondirectories in fs/inode.c
mutex_lock_double in kernel/events/core.c

ep_cmp_ffd in fs/eventpoll.c
fsnotify_compare_groups fs/notify/mark.c

Nothing needs to be done here, since the tags embedded into pointers
don't change, so the sorting order would still be unique.

Checks that a pointer belongs to some particular allocation:

is_sibling_entry in lib/radix-tree.c
object_is_on_stack in include/linux/sched/task_stack.h

Nothing needs to be done here either, since two pointers can only belong
to the same allocation if they have the same tag.

Overall, since the kernel boots and works, there are no critical bugs.
As for the rest, the traditional kernel testing way (use until fails) is
the only one that looks feasible.

Another point here is that tag-based KASAN is available under a separate
config option that needs to be deliberately enabled. Even though it might
be used in a "near-production" environment to find bugs that are not found
during fuzzing or running tests, it is still a debug tool.

====== Benchmarks

The following numbers were collected on Odroid C2 board. Both generic and
tag-based KASAN were used in inline instrumentation mode.

Boot time [1]:
* ~1.7 sec for clean kernel
* ~5.0 sec for generic KASAN
* ~5.0 sec for tag-based KASAN

Network performance [2]:
* 8.33 Gbits/sec for clean kernel
* 3.17 Gbits/sec for generic KASAN
* 2.85 Gbits/sec for tag-based KASAN

Slab memory usage after boot [3]:
* ~40 kb for clean kernel
* ~105 kb (~260% overhead) for generic KASAN
* ~47 kb (~20% overhead) for tag-based KASAN

KASAN memory overhead consists of three main parts:
1. Increased slab memory usage due to redzones.
2. Shadow memory (the whole reserved once during boot).
3. Quaratine (grows gradually until some preset limit; the more the limit,
   the more the chance to detect a use-after-free).

Comparing tag-based vs generic KASAN for each of these points:
1. 20% vs 260% overhead.
2. 1/16th vs 1/8th of physical memory.
3. Tag-based KASAN doesn't require quarantine.

[1] Time before the ext4 driver is initialized.
[2] Measured as `iperf -s & iperf -c 127.0.0.1 -t 30`.
[3] Measured as `cat /proc/meminfo | grep Slab`.

====== Some notes

A few notes:

1. The patchset can be found here:
   https://github.com/xairy/kasan-prototype/tree/khwasan

2. Building requires a recent Clang version (7.0.0 or later).

3. Stack instrumentation is not supported yet and will be added later.

This patch (of 25):

Tag-based KASAN changes the value of the top byte of pointers returned
from the kernel allocation functions (such as kmalloc).  This patch
updates KASAN hooks signatures and their usage in SLAB and SLUB code to
reflect that.

Link: http://lkml.kernel.org/r/aec2b5e3973781ff8a6bb6760f8543643202c451.1544099024.git.andreyknvl@google.comSigned-off-by: NAndrey Konovalov <andreyknvl@google.com>
Reviewed-by: NAndrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: NDmitry Vyukov <dvyukov@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Pull file locking updates from Jeff Layton:
 "The main change in this set is Neil Brown's work to reduce the
  thundering herd problem when a heavily-contended file lock is
  released.

  Previously we'd always wake up all waiters when this occurred. With
  this set, we'll now we only wake up waiters that were blocked on the
  range being released"

* tag 'locks-v4.21-1' of git://git.kernel.org/pub/scm/linux/kernel/git/jlayton/linux:
  locks: Use inode_is_open_for_write
  fs/locks: remove unnecessary white space.
  fs/locks: merge posix_unblock_lock() and locks_delete_block()
  fs/locks: create a tree of dependent requests.
  fs/locks: change all *_conflict() functions to return bool.
  fs/locks: always delete_block after waiting.
  fs/locks: allow a lock request to block other requests.
  fs/locks: use properly initialized file_lock when unlocking.
  ocfs2: properly initial file_lock used for unlock.
  gfs2: properly initial file_lock used for unlock.
  NFS: use locks_copy_lock() to copy locks.
  fs/locks: split out __locks_wake_up_blocks().
  fs/locks: rename some lists and pointers.

Pull ext4 updates from Ted Ts'o:
 "All cleanups and bug fixes; most notably, fix some problems discovered
  in ext4's NFS support, and fix an ioctl (EXT4_IOC_GROUP_ADD) used by
  old versions of e2fsprogs which we accidentally broke a while back.

  Also fixed some error paths in ext4's quota and inline data support.

  Finally, improve tail latency in jbd2's commit code"

* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
  ext4: check for shutdown and r/o file system in ext4_write_inode()
  ext4: force inode writes when nfsd calls commit_metadata()
  ext4: avoid declaring fs inconsistent due to invalid file handles
  ext4: include terminating u32 in size of xattr entries when expanding inodes
  ext4: compare old and new mode before setting update_mode flag
  ext4: fix EXT4_IOC_GROUP_ADD ioctl
  ext4: hard fail dax mount on unsupported devices
  jbd2: update locking documentation for transaction_t
  ext4: remove redundant condition check
  jbd2: clean up indentation issue, replace spaces with tab
  ext4: clean up indentation issues, remove extraneous tabs
  ext4: missing unlock/put_page() in ext4_try_to_write_inline_data()
  ext4: fix possible use after free in ext4_quota_enable
  jbd2: avoid long hold times of j_state_lock while committing a transaction
  ext4: add ext4_sb_bread() to disambiguate ENOMEM cases

Pull iomap update from Darrick Wong:
 "Fix a memory overflow bug for blocksize < pagesize"

* tag 'iomap-4.21-merge-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  iomap: don't search past page end in iomap_is_partially_uptodate

Pull XFS updates from Darrick Wong:

 - Fix CoW remapping of extremely fragmented file areas

 - Fix a zero-length symlink verifier error

 - Constify some of the rmap owner structures for per-AG metadata

 - Precalculate inode geometry for later use

 - Fix scrub counting problems

 - Don't crash when rtsummary inode is null

 - Fix x32 ioctl operation

 - Fix enum->string mappings for ftrace output

 - Cache realtime summary information in memory

* tag 'xfs-4.21-merge-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux: (24 commits)
  xfs: reallocate realtime summary cache on growfs
  xfs: stringify scrub types in ftrace output
  xfs: stringify btree cursor types in ftrace output
  xfs: move XFS_INODE_FORMAT_STR mappings to libxfs
  xfs: move XFS_AG_BTREE_CMP_FORMAT_STR mappings to libxfs
  xfs: fix symbolic enum printing in ftrace output
  xfs: fix function pointer type in ftrace format
  xfs: Fix x32 ioctls when cmd numbers differ from ia32.
  xfs: Fix bulkstat compat ioctls on x32 userspace.
  xfs: Align compat attrlist_by_handle with native implementation.
  xfs: require both realtime inodes to mount
  xfs: cache minimum realtime summary level
  xfs: count inode blocks correctly in inobt scrub
  xfs: precalculate cluster alignment in inodes and blocks
  xfs: precalculate inodes and blocks per inode cluster
  xfs: add a block to inode count converter
  xfs: remove xfs_rmap_ag_owner and friends
  xfs: const-ify xfs_owner_info arguments
  xfs: streamline defer op type handling
  xfs: idiotproof defer op type configuration
  ...

Pull ext2, udf, and quota update from Jan Kara:
 "Some ext2 cleanups, a fix for UDF crash on corrupted media, and one
  quota locking fix"

* tag 'fs_for_4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  quota: Lock s_umount in exclusive mode for Q_XQUOTA{ON,OFF} quotactls.
  udf: Fix BUG on corrupted inode
  ext2: change reusable parameter to true when calling mb_cache_entry_create()
  ext2: remove redundant condition check
  ext2: avoid unnecessary operation in ext2_error()

Pull fsnotify updates from Jan Kara:
 "Support for new FAN_OPEN_EXEC event and couple of cleanups around
  fsnotify"

* tag 'fsnotify_for_v4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  fanotify: Use inode_is_open_for_write
  fanotify: Make sure to check event_len when copying
  fsnotify/fdinfo: include fdinfo.h for inotify_show_fdinfo()
  fanotify: introduce new event mask FAN_OPEN_EXEC_PERM
  fsnotify: refactor fsnotify_parent()/fsnotify() paired calls when event is on path
  fanotify: introduce new event mask FAN_OPEN_EXEC
  fanotify: return only user requested event types in event mask

Pull dlm updates from David Teigland:
 "This set is entirely trivial fixes, mainly around correct cleanup on
  error paths and improved error checks. One patch adds scheduling in a
  potentially long recovery loop"

* tag 'dlm-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/teigland/linux-dlm:
  dlm: fix invalid cluster name warning
  dlm: NULL check before some freeing functions is not needed
  dlm: NULL check before kmem_cache_destroy is not needed
  dlm: fix missing idr_destroy for recover_idr
  dlm: memory leaks on error path in dlm_user_request()
  dlm: lost put_lkb on error path in receive_convert() and receive_unlock()
  dlm: possible memory leak on error path in create_lkb()
  dlm: fixed memory leaks after failed ls_remove_names allocation
  dlm: fix possible call to kfree() for non-initialized pointer
  dlm: Don't swamp the CPU with callbacks queued during recovery
  dlm: don't leak kernel pointer to userspace
  dlm: don't allow zero length names
  dlm: fix invalid free

Pull btrfs updates from David Sterba:
 "New features:

   - swapfile support - after a long time it's here, with some
     limitations where COW design does not work well with the swap
     implementation (nodatacow file, no compression, cannot be
     snapshotted, not possible on multiple devices, ...), as this is the
     most restricted but working setup, we'll try to improve that in the
     future

   - metadata uuid - an optional incompat feature to assign a new
     filesystem UUID without overwriting all metadata blocks, stored
     only in superblock

   - more balance messages are printed to system log, initial is in the
     format of the command line that would be used to start it

  Fixes:

   - tag pages of a snapshot to better separate pages that are involved
     in the snapshot (and need to get synced) from newly dirtied pages
     that could slow down or even livelock the snapshot operation

   - improved check of filesystem id associated with a device during
     scan to detect duplicate devices that could be mixed up during
     mount

   - fix device replace state transitions, eg. when it ends up
     interrupted and reboot tries to restart balance too, or when
     start/cancel ioctls race

   - fix a crash due to a race when quotas are enabled during snapshot
     creation

   - GFP_NOFS/memalloc_nofs_* fixes due to GFP_KERNEL allocations in
     transaction context

   - fix fsync of files with multiple hard links in new directories

   - fix race of send with transaction commits that create snapshots

  Core changes:

   - cleanups:
      * further removals of now-dead fsync code
      * core function for finding free extent has been split and
        provides a base for further cleanups to make the logic more
        understandable
      * removed lot of indirect callbacks for data and metadata inodes
      * simplified refcounting and locking for cloned extent buffers
      * removed redundant function arguments
      * defines converted to enums where appropriate

   - separate reserve for delayed refs from global reserve, update logic
     to do less trickery and ad-hoc heuristics, move out some related
     expensive operations from transaction commit or file truncate

   - dev-replace switched from custom locking scheme to semaphore

   - remove first phase of balance that tried to make some space for the
     relocation by calling shrink and grow, this did not work as
     expected and only introduced more error states due to potential
     resize failures, slightly improves the runtime as the chunks on all
     devices are not needlessly enumerated

   - clone and deduplication now use generic helper that adds a few more
     checks that were missing from the original btrfs implementation of
     the ioctls"

* tag 'for-4.21-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (125 commits)
  btrfs: Fix typos in comments and strings
  btrfs: improve error handling of btrfs_add_link
  Btrfs: use generic_remap_file_range_prep() for cloning and deduplication
  btrfs: Refactor main loop in extent_readpages
  btrfs: Remove 1st shrink/grow phase from balance
  Btrfs: send, fix race with transaction commits that create snapshots
  Btrfs: use nofs context when initializing security xattrs to avoid deadlock
  btrfs: run delayed items before dropping the snapshot
  btrfs: catch cow on deleting snapshots
  btrfs: extent-tree: cleanup one-shot usage of @blocksize in do_walk_down
  Btrfs: scrub, move setup of nofs contexts higher in the stack
  btrfs: scrub: move scrub_setup_ctx allocation out of device_list_mutex
  btrfs: scrub: pass fs_info to scrub_setup_ctx
  btrfs: fix truncate throttling
  btrfs: don't run delayed refs in the end transaction logic
  btrfs: rework btrfs_check_space_for_delayed_refs
  btrfs: add new flushing states for the delayed refs rsv
  btrfs: update may_commit_transaction to use the delayed refs rsv
  btrfs: introduce delayed_refs_rsv
  btrfs: only track ref_heads in delayed_ref_updates
  ...

Pull gfs2 updates from Bob Peterson:

 - Enhancements and performance improvements to journal replay (Abhi
   Das)

 - Cleanup of gfs2_is_ordered and gfs2_is_writeback (Andreas
   Gruenbacher)

 - Fix a potential double-free in inode creation (Andreas Gruenbacher)

 - Fix the bitmap search loop that was searching too far (Andreas
   Gruenbacher)

 - Various cleanups (Andreas Gruenbacher, Bob Peterson)

 - Implement Steve Whitehouse's patch to dump nrpages for inodes (Bob
   Peterson)

 - Fix a withdraw bug where stuffed journaled data files didn't allocate
   enough journal space to be grown (Bob Peterson)

* tag 'gfs2-4.21.fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gfs2/linux-gfs2:
  gfs2: take jdata unstuff into account in do_grow
  gfs2: Dump nrpages for inodes and their glocks
  gfs2: Fix loop in gfs2_rbm_find
  gfs2: Get rid of potential double-freeing in gfs2_create_inode
  gfs2: Remove vestigial bd_ops
  gfs2: read journal in large chunks to locate the head
  gfs2: add a helper function to get_log_header that can be used elsewhere
  gfs2: changes to gfs2_log_XXX_bio
  gfs2: add more timing info to journal recovery process
  gfs2: Fix the gfs2_invalidatepage description
  gfs2: Clean up gfs2_is_{ordered,writeback}

Pull crypto updates from Herbert Xu:
 "API:
   - Add 1472-byte test to tcrypt for IPsec
   - Reintroduced crypto stats interface with numerous changes
   - Support incremental algorithm dumps

  Algorithms:
   - Add xchacha12/20
   - Add nhpoly1305
   - Add adiantum
   - Add streebog hash
   - Mark cts(cbc(aes)) as FIPS allowed

  Drivers:
   - Improve performance of arm64/chacha20
   - Improve performance of x86/chacha20
   - Add NEON-accelerated nhpoly1305
   - Add SSE2 accelerated nhpoly1305
   - Add AVX2 accelerated nhpoly1305
   - Add support for 192/256-bit keys in gcmaes AVX
   - Add SG support in gcmaes AVX
   - ESN for inline IPsec tx in chcr
   - Add support for CryptoCell 703 in ccree
   - Add support for CryptoCell 713 in ccree
   - Add SM4 support in ccree
   - Add SM3 support in ccree
   - Add support for chacha20 in caam/qi2
   - Add support for chacha20 + poly1305 in caam/jr
   - Add support for chacha20 + poly1305 in caam/qi2
   - Add AEAD cipher support in cavium/nitrox"

* 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6: (130 commits)
  crypto: skcipher - remove remnants of internal IV generators
  crypto: cavium/nitrox - Fix build with !CONFIG_DEBUG_FS
  crypto: salsa20-generic - don't unnecessarily use atomic walk
  crypto: skcipher - add might_sleep() to skcipher_walk_virt()
  crypto: x86/chacha - avoid sleeping under kernel_fpu_begin()
  crypto: cavium/nitrox - Added AEAD cipher support
  crypto: mxc-scc - fix build warnings on ARM64
  crypto: api - document missing stats member
  crypto: user - remove unused dump functions
  crypto: chelsio - Fix wrong error counter increments
  crypto: chelsio - Reset counters on cxgb4 Detach
  crypto: chelsio - Handle PCI shutdown event
  crypto: chelsio - cleanup:send addr as value in function argument
  crypto: chelsio - Use same value for both channel in single WR
  crypto: chelsio - Swap location of AAD and IV sent in WR
  crypto: chelsio - remove set but not used variable 'kctx_len'
  crypto: ux500 - Use proper enum in hash_set_dma_transfer
  crypto: ux500 - Use proper enum in cryp_set_dma_transfer
  crypto: aesni - Add scatter/gather avx stubs, and use them in C
  crypto: aesni - Introduce partial block macro
  ..

Pull networking updates from David Miller:

 1) New ipset extensions for matching on destination MAC addresses, from
    Stefano Brivio.

 2) Add ipv4 ttl and tos, plus ipv6 flow label and hop limit offloads to
    nfp driver. From Stefano Brivio.

 3) Implement GRO for plain UDP sockets, from Paolo Abeni.

 4) Lots of work from Michał Mirosław to eliminate the VLAN_TAG_PRESENT
    bit so that we could support the entire vlan_tci value.

 5) Rework the IPSEC policy lookups to better optimize more usecases,
    from Florian Westphal.

 6) Infrastructure changes eliminating direct manipulation of SKB lists
    wherever possible, and to always use the appropriate SKB list
    helpers. This work is still ongoing...

 7) Lots of PHY driver and state machine improvements and
    simplifications, from Heiner Kallweit.

 8) Various TSO deferral refinements, from Eric Dumazet.

 9) Add ntuple filter support to aquantia driver, from Dmitry Bogdanov.

10) Batch dropping of XDP packets in tuntap, from Jason Wang.

11) Lots of cleanups and improvements to the r8169 driver from Heiner
    Kallweit, including support for ->xmit_more. This driver has been
    getting some much needed love since he started working on it.

12) Lots of new forwarding selftests from Petr Machata.

13) Enable VXLAN learning in mlxsw driver, from Ido Schimmel.

14) Packed ring support for virtio, from Tiwei Bie.

15) Add new Aquantia AQtion USB driver, from Dmitry Bezrukov.

16) Add XDP support to dpaa2-eth driver, from Ioana Ciocoi Radulescu.

17) Implement coalescing on TCP backlog queue, from Eric Dumazet.

18) Implement carrier change in tun driver, from Nicolas Dichtel.

19) Support msg_zerocopy in UDP, from Willem de Bruijn.

20) Significantly improve garbage collection of neighbor objects when
    the table has many PERMANENT entries, from David Ahern.

21) Remove egdev usage from nfp and mlx5, and remove the facility
    completely from the tree as it no longer has any users. From Oz
    Shlomo and others.

22) Add a NETDEV_PRE_CHANGEADDR so that drivers can veto the change and
    therefore abort the operation before the commit phase (which is the
    NETDEV_CHANGEADDR event). From Petr Machata.

23) Add indirect call wrappers to avoid retpoline overhead, and use them
    in the GRO code paths. From Paolo Abeni.

24) Add support for netlink FDB get operations, from Roopa Prabhu.

25) Support bloom filter in mlxsw driver, from Nir Dotan.

26) Add SKB extension infrastructure. This consolidates the handling of
    the auxiliary SKB data used by IPSEC and bridge netfilter, and is
    designed to support the needs to MPTCP which could be integrated in
    the future.

27) Lots of XDP TX optimizations in mlx5 from Tariq Toukan.

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next: (1845 commits)
  net: dccp: fix kernel crash on module load
  drivers/net: appletalk/cops: remove redundant if statement and mask
  bnx2x: Fix NULL pointer dereference in bnx2x_del_all_vlans() on some hw
  net/net_namespace: Check the return value of register_pernet_subsys()
  net/netlink_compat: Fix a missing check of nla_parse_nested
  ieee802154: lowpan_header_create check must check daddr
  net/mlx4_core: drop useless LIST_HEAD
  mlxsw: spectrum: drop useless LIST_HEAD
  net/mlx5e: drop useless LIST_HEAD
  iptunnel: Set tun_flags in the iptunnel_metadata_reply from src
  net/mlx5e: fix semicolon.cocci warnings
  staging: octeon: fix build failure with XFRM enabled
  net: Revert recent Spectre-v1 patches.
  can: af_can: Fix Spectre v1 vulnerability
  packet: validate address length if non-zero
  nfc: af_nfc: Fix Spectre v1 vulnerability
  phonet: af_phonet: Fix Spectre v1 vulnerability
  net: core: Fix Spectre v1 vulnerability
  net: minor cleanup in skb_ext_add()
  net: drop the unused helper skb_ext_get()
  ...

Pull modules updates from Jessica Yu:

 - Some modules-related kallsyms cleanups and a kallsyms fix for ARM.

 - Include keys from the secondary keyring in module signature
   verification.

* tag 'modules-for-v4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux:
  ARM: module: Fix function kallsyms on Thumb-2
  module: Overwrite st_size instead of st_info
  module: make it clearer when we're handling kallsyms symbols vs exported symbols
  modsign: use all trusted keys to verify module signature

Pull general security subsystem updates from James Morris:
 "The main changes here are Paul Gortmaker's removal of unneccesary
  module.h infrastructure"

* 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security:
  security: integrity: partial revert of make ima_main explicitly non-modular
  security: fs: make inode explicitly non-modular
  security: audit and remove any unnecessary uses of module.h
  security: integrity: make evm_main explicitly non-modular
  keys: remove needless modular infrastructure from ecryptfs_format
  security: integrity: make ima_main explicitly non-modular
  tomoyo: fix small typo

Pull selinux patches from Paul Moore:
 "I already used my best holiday pull request lines in the audit pull
  request, so this one is going to be a bit more boring, sorry about
  that. To make up for this, we do have a birthday of sorts to
  celebrate: SELinux turns 18 years old this December. Perhaps not the
  most exciting thing in the world for most people, but I think it's
  safe to say that anyone reading this email doesn't exactly fall into
  the "most people" category.

  Back to business and the pull request itself:

  Ondrej has five patches in this pull request and I lump them into
  three categories: one patch to always allow submounts (using similar
  logic to elsewhere in the kernel), one to fix some issues with the
  SELinux policydb, and the others to cleanup and improve the SELinux
  sidtab.

  The other patches from Alexey and Petr and trivial fixes that are
  adequately described in their respective subject lines.

  With this last pull request of the year, I want to thank everyone who
  has contributed patches, testing, and reviews to the SELinux project
  this year, and the past 18 years. Like any good open source effort,
  SELinux is only as good as the community which supports it, and I'm
  very happy that we have the community we do - thank you all!"

* tag 'selinux-pr-20181224' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/selinux:
  selinux: overhaul sidtab to fix bug and improve performance
  selinux: use separate table for initial SID lookup
  selinux: make "selinux_policycap_names[]" const char *
  selinux: always allow mounting submounts
  selinux: refactor sidtab conversion
  Documentation: Update SELinux reference policy URL
  selinux: policydb - fix byte order and alignment issues

Pull audit updates from Paul Moore:
 "In the finest of holiday of traditions, I have a number of gifts to
  share today. While most of them are re-gifts from others, unlike the
  typical re-gift, these are things you will want in and around your
  tree; I promise.

  This pull request is perhaps a bit larger than our typical PR, but
  most of it comes from Jan's rework of audit's fanotify code; a very
  welcome improvement. We ran this through our normal regression tests,
  as well as some newly created stress tests and everything looks good.

  Richard added a few patches, mostly cleaning up a few things and and
  shortening some of the audit records that we send to userspace; a
  change the userspace folks are quite happy about.

  Finally YueHaibing and I kick in a few patches to simplify things a
  bit and make the code less prone to errors.

  Lastly, I want to say thanks one more time to everyone who has
  contributed patches, testing, and code reviews for the audit subsystem
  over the past year. The project is what it is due to your help and
  contributions - thank you"

* tag 'audit-pr-20181224' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit: (22 commits)
  audit: remove duplicated include from audit.c
  audit: shorten PATH cap values when zero
  audit: use current whenever possible
  audit: minimize our use of audit_log_format()
  audit: remove WATCH and TREE config options
  audit: use session_info helper
  audit: localize audit_log_session_info prototype
  audit: Use 'mark' name for fsnotify_mark variables
  audit: Replace chunk attached to mark instead of replacing mark
  audit: Simplify locking around untag_chunk()
  audit: Drop all unused chunk nodes during deletion
  audit: Guarantee forward progress of chunk untagging
  audit: Allocate fsnotify mark independently of chunk
  audit: Provide helper for dropping mark's chunk reference
  audit: Remove pointless check in insert_hash()
  audit: Factor out chunk replacement code
  audit: Make hash table insertion safe against concurrent lookups
  audit: Embed key into chunk
  audit: Fix possible tagging failures
  audit: Fix possible spurious -ENOSPC error
  ...

Pull printk updates from Petr Mladek:

 - Keep spinlocks busted until the end of panic()

 - Fix races between calculating number of messages that would fit into
   user space buffers, filling the buffers, and switching printk.time
   parameter

 - Some code clean up

* tag 'printk-for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk:
  printk: Remove print_prefix() calls with NULL buffer.
  printk: fix printk_time race.
  printk: Make printk_emit() local function.
  panic: avoid deadlocks in re-entrant console drivers

Pull gcc-plugins update from Kees Cook:
 "Both arm and arm64 are gaining per-task stack canaries (to match x86),
  but arm is being done with a gcc plugin, hence it going through the
  gcc-plugins tree.

  New gcc-plugin:

   - Enable per-task stack protector for ARM (Ard Biesheuvel)"

* tag 'gcc-plugins-v4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  ARM: smp: add support for per-task stack canaries

Pull pstore updates from Kees Cook:
 "Improvements and refactorings:

   - Improve compression handling

   - Refactor argument handling during initialization

   - Avoid needless locking for saner EFI backend handling

   - Add more kern-doc and improve debugging output"

* tag 'pstore-v4.21-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  pstore/ram: Avoid NULL deref in ftrace merging failure path
  pstore: Convert buf_lock to semaphore
  pstore: Fix bool initialization/comparison
  pstore/ram: Do not treat empty buffers as valid
  pstore/ram: Simplify ramoops_get_next_prz() arguments
  pstore: Map PSTORE_TYPE_* to strings
  pstore: Replace open-coded << with BIT()
  pstore: Improve and update some comments and status output
  pstore/ram: Add kern-doc for struct persistent_ram_zone
  pstore/ram: Report backend assignments with finer granularity
  pstore/ram: Standardize module name in ramoops
  pstore: Avoid duplicate call of persistent_ram_zap()
  pstore: Remove needless lock during console writes
  pstore: Do not use crash buffer for decompression

Pull powerpc updates from Michael Ellerman:
 "Notable changes:

   - Mitigations for Spectre v2 on some Freescale (NXP) CPUs.

   - A large series adding support for pass-through of Nvidia V100 GPUs
     to guests on Power9.

   - Another large series to enable hardware assistance for TLB table
     walk on MPC8xx CPUs.

   - Some preparatory changes to our DMA code, to make way for further
     cleanups from Christoph.

   - Several fixes for our Transactional Memory handling discovered by
     fuzzing the signal return path.

   - Support for generating our system call table(s) from a text file
     like other architectures.

   - A fix to our page fault handler so that instead of generating a
     WARN_ON_ONCE, user accesses of kernel addresses instead print a
     ratelimited and appropriately scary warning.

   - A cosmetic change to make our unhandled page fault messages more
     similar to other arches and also more compact and informative.

   - Freescale updates from Scott:
       "Highlights include elimination of legacy clock bindings use from
        dts files, an 83xx watchdog handler, fixes to old dts interrupt
        errors, and some minor cleanup."

  And many clean-ups, reworks and minor fixes etc.

  Thanks to: Alexandre Belloni, Alexey Kardashevskiy, Andrew Donnellan,
  Aneesh Kumar K.V, Arnd Bergmann, Benjamin Herrenschmidt, Breno Leitao,
  Christian Lamparter, Christophe Leroy, Christoph Hellwig, Daniel
  Axtens, Darren Stevens, David Gibson, Diana Craciun, Dmitry V. Levin,
  Firoz Khan, Geert Uytterhoeven, Greg Kurz, Gustavo Romero, Hari
  Bathini, Joel Stanley, Kees Cook, Madhavan Srinivasan, Mahesh
  Salgaonkar, Markus Elfring, Mathieu Malaterre, Michal Suchánek, Naveen
  N. Rao, Nick Desaulniers, Oliver O'Halloran, Paul Mackerras, Ram Pai,
  Ravi Bangoria, Rob Herring, Russell Currey, Sabyasachi Gupta, Sam
  Bobroff, Satheesh Rajendran, Scott Wood, Segher Boessenkool, Stephen
  Rothwell, Tang Yuantian, Thiago Jung Bauermann, Yangtao Li, Yuantian
  Tang, Yue Haibing"

* tag 'powerpc-4.21-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (201 commits)
  Revert "powerpc/fsl_pci: simplify fsl_pci_dma_set_mask"
  powerpc/zImage: Also check for stdout-path
  powerpc: Fix HMIs on big-endian with CONFIG_RELOCATABLE=y
  macintosh: Use of_node_name_{eq, prefix} for node name comparisons
  ide: Use of_node_name_eq for node name comparisons
  powerpc: Use of_node_name_eq for node name comparisons
  powerpc/pseries/pmem: Convert to %pOFn instead of device_node.name
  powerpc/mm: Remove very old comment in hash-4k.h
  powerpc/pseries: Fix node leak in update_lmb_associativity_index()
  powerpc/configs/85xx: Enable CONFIG_DEBUG_KERNEL
  powerpc/dts/fsl: Fix dtc-flagged interrupt errors
  clk: qoriq: add more compatibles strings
  powerpc/fsl: Use new clockgen binding
  powerpc/83xx: handle machine check caused by watchdog timer
  powerpc/fsl-rio: fix spelling mistake "reserverd" -> "reserved"
  powerpc/fsl_pci: simplify fsl_pci_dma_set_mask
  arch/powerpc/fsl_rmu: Use dma_zalloc_coherent
  vfio_pci: Add NVIDIA GV100GL [Tesla V100 SXM2] subdriver
  vfio_pci: Allow regions to add own capabilities
  vfio_pci: Allow mapping extra regions
  ...

Caused by making the variable static:

  kernel/sched/fair.c:119:21: warning: 'capacity_margin' defined but not used [-Wunused-variable]

Seems easiest to just move it up under the existing ifdef CONFIG_SMP
that's a few lines above.

Fixes: ed8885a1 ('sched/fair: Make some variables static')
Signed-off-by: NOlof Johansson <olof@lixom.net>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Pull x86 platform update from Ingo Molnar:
 "An OLPC platform support simplification patch"

* 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/platform/olpc: Do not call of_platform_bus_probe()

Pull x86 mm updates from Ingo Molnar:
 "The main changes in this cycle were:

   - Update and clean up x86 fault handling, by Andy Lutomirski.

   - Drop usage of __flush_tlb_all() in kernel_physical_mapping_init()
     and related fallout, by Dan Williams.

   - CPA cleanups and reorganization by Peter Zijlstra: simplify the
     flow and remove a few warts.

   - Other misc cleanups"

* 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (29 commits)
  x86/mm/dump_pagetables: Use DEFINE_SHOW_ATTRIBUTE()
  x86/mm/cpa: Rename @addrinarray to @numpages
  x86/mm/cpa: Better use CLFLUSHOPT
  x86/mm/cpa: Fold cpa_flush_range() and cpa_flush_array() into a single cpa_flush() function
  x86/mm/cpa: Make cpa_data::numpages invariant
  x86/mm/cpa: Optimize cpa_flush_array() TLB invalidation
  x86/mm/cpa: Simplify the code after making cpa->vaddr invariant
  x86/mm/cpa: Make cpa_data::vaddr invariant
  x86/mm/cpa: Add __cpa_addr() helper
  x86/mm/cpa: Add ARRAY and PAGES_ARRAY selftests
  x86/mm: Drop usage of __flush_tlb_all() in kernel_physical_mapping_init()
  x86/mm: Validate kernel_physical_mapping_init() PTE population
  generic/pgtable: Introduce set_pte_safe()
  generic/pgtable: Introduce {p4d,pgd}_same()
  generic/pgtable: Make {pmd, pud}_same() unconditionally available
  x86/fault: Clean up the page fault oops decoder a bit
  x86/fault: Decode page fault OOPSes better
  x86/vsyscall/64: Use X86_PF constants in the simulated #PF error code
  x86/oops: Show the correct CS value in show_regs()
  x86/fault: Don't try to recover from an implicit supervisor access
  ...