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  1. 03 11月, 2017 1 次提交
    • D
      mm: introduce MAP_SHARED_VALIDATE, a mechanism to safely define new mmap flags · 1c972597
      由 Dan Williams 提交于 
      The mmap(2) syscall suffers from the ABI anti-pattern of not validating
unknown flags. However, proposals like MAP_SYNC need a mechanism to
define new behavior that is known to fail on older kernels without the
support. Define a new MAP_SHARED_VALIDATE flag pattern that is
guaranteed to fail on all legacy mmap implementations.

It is worth noting that the original proposal was for a standalone
MAP_VALIDATE flag. However, when that  could not be supported by all
archs Linus observed:

    I see why you *think* you want a bitmap. You think you want
    a bitmap because you want to make MAP_VALIDATE be part of MAP_SYNC
    etc, so that people can do

    ret = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED
		    | MAP_SYNC, fd, 0);

    and "know" that MAP_SYNC actually takes.

    And I'm saying that whole wish is bogus. You're fundamentally
    depending on special semantics, just make it explicit. It's already
    not portable, so don't try to make it so.

    Rename that MAP_VALIDATE as MAP_SHARED_VALIDATE, make it have a value
    of 0x3, and make people do

    ret = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED_VALIDATE
		    | MAP_SYNC, fd, 0);

    and then the kernel side is easier too (none of that random garbage
    playing games with looking at the "MAP_VALIDATE bit", but just another
    case statement in that map type thing.

    Boom. Done.

Similar to ->fallocate() we also want the ability to validate the
support for new flags on a per ->mmap() 'struct file_operations'
instance basis.  Towards that end arrange for flags to be generically
validated against a mmap_supported_flags exported by 'struct
file_operations'. By default all existing flags are implicitly
supported, but new flags require MAP_SHARED_VALIDATE and
per-instance-opt-in.

Cc: Jan Kara <jack@suse.cz>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: NChristoph Hellwig <hch@lst.de>
Suggested-by: NLinus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: NRoss Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NDan Williams <dan.j.williams@intel.com>
      1c972597
  3. 09 9月, 2017 1 次提交
  5. 07 9月, 2017 3 次提交
  7. 15 7月, 2017 1 次提交
  9. 11 7月, 2017 3 次提交
  11. 07 7月, 2017 1 次提交
  13. 22 6月, 2017 2 次提交
  15. 21 6月, 2017 1 次提交
    • D
      ARM: 8683/1: ARM32: Support mremap() for sigpage/vDSO · 280e87e9
      由 Dmitry Safonov 提交于 
      CRIU restores application mappings on the same place where they
were before Checkpoint. That means, that we need to move vDSO
and sigpage during restore on exactly the same place where
they were before C/R.

Make mremap() code update mm->context.{sigpage,vdso} pointers
during VMA move. Sigpage is used for landing after handling
a signal - if the pointer is not updated during moving, the
application might crash on any signal after mremap().

vDSO pointer on ARM32 is used only for setting auxv at this moment,
update it during mremap() in case of future usage.

Without those updates, current work of CRIU on ARM32 is not reliable.
Historically, we error Checkpointing if we find vDSO page on ARM32
and suggest user to disable CONFIG_VDSO.
But that's not correct - it goes from x86 where signal processing
is ended in vDSO blob. For arm32 it's sigpage, which is not disabled
with `CONFIG_VDSO=n'.

Looks like C/R was working by luck - because userspace on ARM32 at
this moment always sets SA_RESTORER.
Signed-off-by: NDmitry Safonov <dsafonov@virtuozzo.com>
Acked-by: NAndy Lutomirski <luto@amacapital.net>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Will Deacon <will.deacon@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Cc: Christopher Covington <cov@codeaurora.org>
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>
      280e87e9
  17. 19 6月, 2017 1 次提交
    • H
      mm: larger stack guard gap, between vmas · 1be7107f
      由 Hugh Dickins 提交于 
      Stack guard page is a useful feature to reduce a risk of stack smashing
into a different mapping. We have been using a single page gap which
is sufficient to prevent having stack adjacent to a different mapping.
But this seems to be insufficient in the light of the stack usage in
userspace. E.g. glibc uses as large as 64kB alloca() in many commonly
used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX]
which is 256kB or stack strings with MAX_ARG_STRLEN.

This will become especially dangerous for suid binaries and the default
no limit for the stack size limit because those applications can be
tricked to consume a large portion of the stack and a single glibc call
could jump over the guard page. These attacks are not theoretical,
unfortunatelly.

Make those attacks less probable by increasing the stack guard gap
to 1MB (on systems with 4k pages; but make it depend on the page size
because systems with larger base pages might cap stack allocations in
the PAGE_SIZE units) which should cover larger alloca() and VLA stack
allocations. It is obviously not a full fix because the problem is
somehow inherent, but it should reduce attack space a lot.

One could argue that the gap size should be configurable from userspace,
but that can be done later when somebody finds that the new 1MB is wrong
for some special case applications.  For now, add a kernel command line
option (stack_guard_gap) to specify the stack gap size (in page units).

Implementation wise, first delete all the old code for stack guard page:
because although we could get away with accounting one extra page in a
stack vma, accounting a larger gap can break userspace - case in point,
a program run with "ulimit -S -v 20000" failed when the 1MB gap was
counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK
and strict non-overcommit mode.

Instead of keeping gap inside the stack vma, maintain the stack guard
gap as a gap between vmas: using vm_start_gap() in place of vm_start
(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few
places which need to respect the gap - mainly arch_get_unmapped_area(),
and and the vma tree's subtree_gap support for that.
Original-patch-by: NOleg Nesterov <oleg@redhat.com>
Original-patch-by: NMichal Hocko <mhocko@suse.com>
Signed-off-by: NHugh Dickins <hughd@google.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Tested-by: Helge Deller <deller@gmx.de> # parisc
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      1be7107f
  19. 04 5月, 2017 1 次提交
  21. 25 2月, 2017 5 次提交
  23. 23 2月, 2017 1 次提交
    • D
      powerpc: do not make the entire heap executable · 16e72e9b
      由 Denys Vlasenko 提交于 
      On 32-bit powerpc the ELF PLT sections of binaries (built with
--bss-plt, or with a toolchain which defaults to it) look like this:

  [17] .sbss             NOBITS          0002aff8 01aff8 000014 00  WA  0   0  4
  [18] .plt              NOBITS          0002b00c 01aff8 000084 00 WAX  0   0  4
  [19] .bss              NOBITS          0002b090 01aff8 0000a4 00  WA  0   0  4

Which results in an ELF load header:

  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
  LOAD           0x019c70 0x00029c70 0x00029c70 0x01388 0x014c4 RWE 0x10000

This is all correct, the load region containing the PLT is marked as
executable.  Note that the PLT starts at 0002b00c but the file mapping
ends at 0002aff8, so the PLT falls in the 0 fill section described by
the load header, and after a page boundary.

Unfortunately the generic ELF loader ignores the X bit in the load
headers when it creates the 0 filled non-file backed mappings.  It
assumes all of these mappings are RW BSS sections, which is not the case
for PPC.

gcc/ld has an option (--secure-plt) to not do this, this is said to
incur a small performance penalty.

Currently, to support 32-bit binaries with PLT in BSS kernel maps
*entire brk area* with executable rights for all binaries, even
--secure-plt ones.

Stop doing that.

Teach the ELF loader to check the X bit in the relevant load header and
create 0 filled anonymous mappings that are executable if the load
header requests that.

Test program showing the difference in /proc/$PID/maps:

int main() {
	char buf[16*1024];
	char *p = malloc(123); /* make "[heap]" mapping appear */
	int fd = open("/proc/self/maps", O_RDONLY);
	int len = read(fd, buf, sizeof(buf));
	write(1, buf, len);
	printf("%p\n", p);
	return 0;
}

Compiled using: gcc -mbss-plt -m32 -Os test.c -otest

Unpatched ppc64 kernel:
00100000-00120000 r-xp 00000000 00:00 0                                  [vdso]
0fe10000-0ffd0000 r-xp 00000000 fd:00 67898094                           /usr/lib/libc-2.17.so
0ffd0000-0ffe0000 r--p 001b0000 fd:00 67898094                           /usr/lib/libc-2.17.so
0ffe0000-0fff0000 rw-p 001c0000 fd:00 67898094                           /usr/lib/libc-2.17.so
10000000-10010000 r-xp 00000000 fd:00 100674505                          /home/user/test
10010000-10020000 r--p 00000000 fd:00 100674505                          /home/user/test
10020000-10030000 rw-p 00010000 fd:00 100674505                          /home/user/test
10690000-106c0000 rwxp 00000000 00:00 0                                  [heap]
f7f70000-f7fa0000 r-xp 00000000 fd:00 67898089                           /usr/lib/ld-2.17.so
f7fa0000-f7fb0000 r--p 00020000 fd:00 67898089                           /usr/lib/ld-2.17.so
f7fb0000-f7fc0000 rw-p 00030000 fd:00 67898089                           /usr/lib/ld-2.17.so
ffa90000-ffac0000 rw-p 00000000 00:00 0                                  [stack]
0x10690008

Patched ppc64 kernel:
00100000-00120000 r-xp 00000000 00:00 0                                  [vdso]
0fe10000-0ffd0000 r-xp 00000000 fd:00 67898094                           /usr/lib/libc-2.17.so
0ffd0000-0ffe0000 r--p 001b0000 fd:00 67898094                           /usr/lib/libc-2.17.so
0ffe0000-0fff0000 rw-p 001c0000 fd:00 67898094                           /usr/lib/libc-2.17.so
10000000-10010000 r-xp 00000000 fd:00 100674505                          /home/user/test
10010000-10020000 r--p 00000000 fd:00 100674505                          /home/user/test
10020000-10030000 rw-p 00010000 fd:00 100674505                          /home/user/test
10180000-101b0000 rw-p 00000000 00:00 0                                  [heap]
                  ^^^^ this has changed
f7c60000-f7c90000 r-xp 00000000 fd:00 67898089                           /usr/lib/ld-2.17.so
f7c90000-f7ca0000 r--p 00020000 fd:00 67898089                           /usr/lib/ld-2.17.so
f7ca0000-f7cb0000 rw-p 00030000 fd:00 67898089                           /usr/lib/ld-2.17.so
ff860000-ff890000 rw-p 00000000 00:00 0                                  [stack]
0x10180008

The patch was originally posted in 2012 by Jason Gunthorpe
and apparently ignored:

https://lkml.org/lkml/2012/9/30/138

Lightly run-tested.

Link: http://lkml.kernel.org/r/20161215131950.23054-1-dvlasenk@redhat.comSigned-off-by: NJason Gunthorpe <jgunthorpe@obsidianresearch.com>
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Acked-by: NKees Cook <keescook@chromium.org>
Acked-by: NMichael Ellerman <mpe@ellerman.id.au>
Tested-by: NJason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Florian Weimer <fweimer@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      16e72e9b
  25. 20 2月, 2017 1 次提交
  27. 25 12月, 2016 1 次提交
  29. 08 10月, 2016 6 次提交
  31. 15 9月, 2016 1 次提交
  33. 26 8月, 2016 1 次提交
    • C
      arm64: Introduce execute-only page access permissions · cab15ce6
      由 Catalin Marinas 提交于 
      The ARMv8 architecture allows execute-only user permissions by clearing
the PTE_UXN and PTE_USER bits. However, the kernel running on a CPU
implementation without User Access Override (ARMv8.2 onwards) can still
access such page, so execute-only page permission does not protect
against read(2)/write(2) etc. accesses. Systems requiring such
protection must enable features like SECCOMP.

This patch changes the arm64 __P100 and __S100 protection_map[] macros
to the new __PAGE_EXECONLY attributes. A side effect is that
pte_user() no longer triggers for __PAGE_EXECONLY since PTE_USER isn't
set. To work around this, the check is done on the PTE_NG bit via the
pte_ng() macro. VM_READ is also checked now for page faults.
Reviewed-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
      cab15ce6
  35. 03 8月, 2016 1 次提交
  37. 29 7月, 2016 1 次提交
  39. 27 7月, 2016 3 次提交
  41. 08 7月, 2016 1 次提交
    • D
      x86/vdso: Add mremap hook to vm_special_mapping · b059a453
      由 Dmitry Safonov 提交于 
      Add possibility for 32-bit user-space applications to move
the vDSO mapping.

Previously, when a user-space app called mremap() for the vDSO
address, in the syscall return path it would land on the previous
address of the vDSOpage, resulting in segmentation violation.

Now it lands fine and returns to userspace with a remapped vDSO.

This will also fix the context.vdso pointer for 64-bit, which does
not affect the user of vDSO after mremap() currently, but this
may change in the future.

As suggested by Andy, return -EINVAL for mremap() that would
split the vDSO image: that operation cannot possibly result in
a working system so reject it.

Renamed and moved the text_mapping structure declaration inside
map_vdso(), as it used only there and now it complements the
vvar_mapping variable.

There is still a problem for remapping the vDSO in glibc
applications: the linker relocates addresses for syscalls
on the vDSO page, so you need to relink with the new
addresses.

Without that the next syscall through glibc may fail:

  Program received signal SIGSEGV, Segmentation fault.
  #0  0xf7fd9b80 in __kernel_vsyscall ()
  #1  0xf7ec8238 in _exit () from /usr/lib32/libc.so.6
Signed-off-by: NDmitry Safonov <dsafonov@virtuozzo.com>
Acked-by: NAndy Lutomirski <luto@kernel.org>
Cc: 0x7f454c46@gmail.com
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20160628113539.13606-2-dsafonov@virtuozzo.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      b059a453
  43. 28 5月, 2016 1 次提交
    • L
      mm: remove more IS_ERR_VALUE abuses · 5d22fc25
      由 Linus Torvalds 提交于 
      The do_brk() and vm_brk() return value was "unsigned long" and returned
the starting address on success, and an error value on failure.  The
reasons are entirely historical, and go back to it basically behaving
like the mmap() interface does.

However, nobody actually wanted that interface, and it causes totally
pointless IS_ERR_VALUE() confusion.

What every single caller actually wants is just the simpler integer
return of zero for success and negative error number on failure.

So just convert to that much clearer and more common calling convention,
and get rid of all the IS_ERR_VALUE() uses wrt vm_brk().
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      5d22fc25
  45. 24 5月, 2016 2 次提交
    • M
      mm: make vm_brk killable · 2d6c9282
      由 Michal Hocko 提交于 
      Now that all the callers handle vm_brk failure we can change it wait for
mmap_sem killable to help oom_reaper to not get blocked just because
vm_brk gets blocked behind mmap_sem readers.
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Acked-by: NVlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      2d6c9282
    • M
      mm: make vm_munmap killable · ae798783
      由 Michal Hocko 提交于 
      Almost all current users of vm_munmap are ignoring the return value and
so they do not handle potential error.  This means that some VMAs might
stay behind.  This patch doesn't try to solve those potential problems.
Quite contrary it adds a new failure mode by using down_write_killable
in vm_munmap.  This should be safer than other failure modes, though,
because the process is guaranteed to die as soon as it leaves the kernel
and exit_mmap will clean the whole address space.

This will help in the OOM conditions when the oom victim might be stuck
waiting for the mmap_sem for write which in turn can block oom_reaper
which relies on the mmap_sem for read to make a forward progress and
reclaim the address space of the victim.
Signed-off-by: NMichal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      ae798783