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  1. 05 6月, 2018 1 次提交
    • L
      swait: strengthen language to discourage use · c5e7a7ea
      由 Linus Torvalds 提交于 
      We already earlier discouraged people from using this interface in
commit 88796e7e ("sched/swait: Document it clearly that the swait
facilities are special and shouldn't be used"), but I just got a pull
request with a new broken user.

So make the comment *really* clear.

The swait interfaces are bad, and should not be used unless you have
some *very* strong reasons that include tons of hard performance numbers
on just why you want to use them, and you show that you actually
understand that they aren't at all like the normal wait/wakeup
interfaces.

So far, every single user has been suspect.  The main user is KVM, which
is completely pointless (there is only ever one waiter, which avoids the
interface subtleties, but also means that having a queue instead of a
pointer is counter-productive and certainly not an "optimization").

So make the comments much stronger.

Not that anybody likely reads them anyway, but there's always some
slight hope that it will cause somebody to think twice.

I'd like to remove this interface entirely, but there is the theoretical
possibility that it's actually the right thing to use in some situation,
most likely some deep RT use.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      c5e7a7ea
  3. 03 6月, 2018 1 次提交
    • J
      block: don't use blocking queue entered for recursive bio submits · cd4a4ae4
      由 Jens Axboe 提交于 
      If we end up splitting a bio and the queue goes away between
the initial submission and the later split submission, then we
can block forever in blk_queue_enter() waiting for the reference
to drop to zero. This will never happen, since we already hold
a reference.

Mark a split bio as already having entered the queue, so we can
just use the live non-blocking queue enter variant.

Thanks to Tetsuo Handa for the analysis.

Reported-by: syzbot+c4f9cebf9d651f6e54de@syzkaller.appspotmail.com
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      cd4a4ae4
  5. 01 6月, 2018 5 次提交
  7. 31 5月, 2018 5 次提交
  9. 30 5月, 2018 1 次提交
  11. 29 5月, 2018 8 次提交
  13. 28 5月, 2018 2 次提交
  15. 26 5月, 2018 9 次提交
  17. 25 5月, 2018 5 次提交
    • H
      dma-mapping: remove unused gfp_t parameter to arch_dma_alloc_attrs · 884571f0
      由 Huaisheng Ye 提交于 
      Signed-off-by: NHuaisheng Ye <yehs1@lenovo.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
      884571f0
    • S
      perf/core: Fix bad use of igrab() · 9511bce9
      由 Song Liu 提交于 
      As Miklos reported and suggested:

 "This pattern repeats two times in trace_uprobe.c and in
  kernel/events/core.c as well:

      ret = kern_path(filename, LOOKUP_FOLLOW, &path);
      if (ret)
          goto fail_address_parse;

      inode = igrab(d_inode(path.dentry));
      path_put(&path);

  And it's wrong.  You can only hold a reference to the inode if you
  have an active ref to the superblock as well (which is normally
  through path.mnt) or holding s_umount.

  This way unmounting the containing filesystem while the tracepoint is
  active will give you the "VFS: Busy inodes after unmount..." message
  and a crash when the inode is finally put.

  Solution: store path instead of inode."

This patch fixes the issue in kernel/event/core.c.
Reviewed-and-tested-by: NAlexander Shishkin <alexander.shishkin@linux.intel.com>
Reported-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NSong Liu <songliubraving@fb.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: <kernel-team@fb.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: 375637bc ("perf/core: Introduce address range filtering")
Link: http://lkml.kernel.org/r/20180418062907.3210386-2-songliubraving@fb.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      9511bce9
    • S
      perf/core: Fix group scheduling with mixed hw and sw events · a1150c20
      由 Song Liu 提交于 
      When hw and sw events are mixed in the same group, they are all attached
to the hw perf_event_context. This sometimes requires moving group of
perf_event to a different context.

We found a bug in how the kernel handles this, for example if we do:

   perf stat -e '{faults,ref-cycles,faults}'  -I 1000

     1.005591180              1,297      faults
     1.005591180        457,476,576      ref-cycles
     1.005591180    <not supported>      faults

First, sw event "faults" is attached to the sw context, and becomes the
group leader. Then, hw event "ref-cycles" is attached, so both events
are moved to the hw context. Last, another sw "faults" tries to attach,
but it fails because of mismatch between the new target ctx (from sw
pmu) and the group_leader's ctx (hw context, same as ref-cycles).

The broken condition is:
   group_leader is sw event;
   group_leader is on hw context;
   add a sw event to the group.

Fix this scenario by checking group_leader's context (instead of just
event type). If group_leader is on hw context, use the ->pmu of this
context to look up context for the new event.
Signed-off-by: NSong Liu <songliubraving@fb.com>
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: <kernel-team@fb.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: b04243ef ("perf: Complete software pmu grouping")
Link: http://lkml.kernel.org/r/20180503194716.162815-1-songliubraving@fb.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      a1150c20
    • J
      Revert "mm/cma: manage the memory of the CMA area by using the ZONE_MOVABLE" · d883c6cf
      由 Joonsoo Kim 提交于 
      This reverts the following commits that change CMA design in MM.

 3d2054ad ("ARM: CMA: avoid double mapping to the CMA area if CONFIG_HIGHMEM=y")

 1d47a3ec ("mm/cma: remove ALLOC_CMA")

 bad8c6c0 ("mm/cma: manage the memory of the CMA area by using the ZONE_MOVABLE")

Ville reported a following error on i386.

  Inode-cache hash table entries: 65536 (order: 6, 262144 bytes)
  microcode: microcode updated early to revision 0x4, date = 2013-06-28
  Initializing CPU#0
  Initializing HighMem for node 0 (000377fe:00118000)
  Initializing Movable for node 0 (00000001:00118000)
  BUG: Bad page state in process swapper  pfn:377fe
  page:f53effc0 count:0 mapcount:-127 mapping:00000000 index:0x0
  flags: 0x80000000()
  raw: 80000000 00000000 00000000 ffffff80 00000000 00000100 00000200 00000001
  page dumped because: nonzero mapcount
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper Not tainted 4.17.0-rc5-elk+ #145
  Hardware name: Dell Inc. Latitude E5410/03VXMC, BIOS A15 07/11/2013
  Call Trace:
   dump_stack+0x60/0x96
   bad_page+0x9a/0x100
   free_pages_check_bad+0x3f/0x60
   free_pcppages_bulk+0x29d/0x5b0
   free_unref_page_commit+0x84/0xb0
   free_unref_page+0x3e/0x70
   __free_pages+0x1d/0x20
   free_highmem_page+0x19/0x40
   add_highpages_with_active_regions+0xab/0xeb
   set_highmem_pages_init+0x66/0x73
   mem_init+0x1b/0x1d7
   start_kernel+0x17a/0x363
   i386_start_kernel+0x95/0x99
   startup_32_smp+0x164/0x168

The reason for this error is that the span of MOVABLE_ZONE is extended
to whole node span for future CMA initialization, and, normal memory is
wrongly freed here.  I submitted the fix and it seems to work, but,
another problem happened.

It's so late time to fix the later problem so I decide to reverting the
series.
Reported-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: NLaura Abbott <labbott@redhat.com>
Acked-by: NMichal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJoonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d883c6cf
    • M
      blk-mq: avoid starving tag allocation after allocating process migrates · e6fc4649
      由 Ming Lei 提交于 
      When the allocation process is scheduled back and the mapped hw queue is
changed, fake one extra wake up on previous queue for compensating wake
up miss, so other allocations on the previous queue won't be starved.

This patch fixes one request allocation hang issue, which can be
triggered easily in case of very low nr_request.

The race is as follows:

1) 2 hw queues, nr_requests are 2, and wake_batch is one

2) there are 3 waiters on hw queue 0

3) two in-flight requests in hw queue 0 are completed, and only two
   waiters of 3 are waken up because of wake_batch, but both the two
   waiters can be scheduled to another CPU and cause to switch to hw
   queue 1

4) then the 3rd waiter will wait for ever, since no in-flight request
   is in hw queue 0 any more.

5) this patch fixes it by the fake wakeup when waiter is scheduled to
   another hw queue

Cc: <stable@vger.kernel.org>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NMing Lei <ming.lei@redhat.com>

Modified commit message to make it clearer, and make it apply on
top of the 4.18 branch.
Signed-off-by: NJens Axboe <axboe@kernel.dk>
      e6fc4649
  19. 24 5月, 2018 1 次提交
    • D
      bpf: properly enforce index mask to prevent out-of-bounds speculation · c93552c4
      由 Daniel Borkmann 提交于 
      While reviewing the verifier code, I recently noticed that the
following two program variants in relation to tail calls can be
loaded.

Variant 1:

  # bpftool p d x i 15
    0: (15) if r1 == 0x0 goto pc+3
    1: (18) r2 = map[id:5]
    3: (05) goto pc+2
    4: (18) r2 = map[id:6]
    6: (b7) r3 = 7
    7: (35) if r3 >= 0xa0 goto pc+2
    8: (54) (u32) r3 &= (u32) 255
    9: (85) call bpf_tail_call#12
   10: (b7) r0 = 1
   11: (95) exit

  # bpftool m s i 5
    5: prog_array  flags 0x0
        key 4B  value 4B  max_entries 4  memlock 4096B
  # bpftool m s i 6
    6: prog_array  flags 0x0
        key 4B  value 4B  max_entries 160  memlock 4096B

Variant 2:

  # bpftool p d x i 20
    0: (15) if r1 == 0x0 goto pc+3
    1: (18) r2 = map[id:8]
    3: (05) goto pc+2
    4: (18) r2 = map[id:7]
    6: (b7) r3 = 7
    7: (35) if r3 >= 0x4 goto pc+2
    8: (54) (u32) r3 &= (u32) 3
    9: (85) call bpf_tail_call#12
   10: (b7) r0 = 1
   11: (95) exit

  # bpftool m s i 8
    8: prog_array  flags 0x0
        key 4B  value 4B  max_entries 160  memlock 4096B
  # bpftool m s i 7
    7: prog_array  flags 0x0
        key 4B  value 4B  max_entries 4  memlock 4096B

In both cases the index masking inserted by the verifier in order
to control out of bounds speculation from a CPU via b2157399
("bpf: prevent out-of-bounds speculation") seems to be incorrect
in what it is enforcing. In the 1st variant, the mask is applied
from the map with the significantly larger number of entries where
we would allow to a certain degree out of bounds speculation for
the smaller map, and in the 2nd variant where the mask is applied
from the map with the smaller number of entries, we get buggy
behavior since we truncate the index of the larger map.

The original intent from commit b2157399 is to reject such
occasions where two or more different tail call maps are used
in the same tail call helper invocation. However, the check on
the BPF_MAP_PTR_POISON is never hit since we never poisoned the
saved pointer in the first place! We do this explicitly for map
lookups but in case of tail calls we basically used the tail
call map in insn_aux_data that was processed in the most recent
path which the verifier walked. Thus any prior path that stored
a pointer in insn_aux_data at the helper location was always
overridden.

Fix it by moving the map pointer poison logic into a small helper
that covers both BPF helpers with the same logic. After that in
fixup_bpf_calls() the poison check is then hit for tail calls
and the program rejected. Latter only happens in unprivileged
case since this is the *only* occasion where a rewrite needs to
happen, and where such rewrite is specific to the map (max_entries,
index_mask). In the privileged case the rewrite is generic for
the insn->imm / insn->code update so multiple maps from different
paths can be handled just fine since all the remaining logic
happens in the instruction processing itself. This is similar
to the case of map lookups: in case there is a collision of
maps in fixup_bpf_calls() we must skip the inlined rewrite since
this will turn the generic instruction sequence into a non-
generic one. Thus the patch_call_imm will simply update the
insn->imm location where the bpf_map_lookup_elem() will later
take care of the dispatch. Given we need this 'poison' state
as a check, the information of whether a map is an unpriv_array
gets lost, so enforcing it prior to that needs an additional
state. In general this check is needed since there are some
complex and tail call intensive BPF programs out there where
LLVM tends to generate such code occasionally. We therefore
convert the map_ptr rather into map_state to store all this
w/o extra memory overhead, and the bit whether one of the maps
involved in the collision was from an unpriv_array thus needs
to be retained as well there.

Fixes: b2157399 ("bpf: prevent out-of-bounds speculation")
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
      c93552c4
  21. 23 5月, 2018 1 次提交
  23. 20 5月, 2018 1 次提交
    • A
      bpf: Prevent memory disambiguation attack · af86ca4e
      由 Alexei Starovoitov 提交于 
      Detect code patterns where malicious 'speculative store bypass' can be used
and sanitize such patterns.

 39: (bf) r3 = r10
 40: (07) r3 += -216
 41: (79) r8 = *(u64 *)(r7 +0)   // slow read
 42: (7a) *(u64 *)(r10 -72) = 0  // verifier inserts this instruction
 43: (7b) *(u64 *)(r8 +0) = r3   // this store becomes slow due to r8
 44: (79) r1 = *(u64 *)(r6 +0)   // cpu speculatively executes this load
 45: (71) r2 = *(u8 *)(r1 +0)    // speculatively arbitrary 'load byte'
                                 // is now sanitized

Above code after x86 JIT becomes:
 e5: mov    %rbp,%rdx
 e8: add    $0xffffffffffffff28,%rdx
 ef: mov    0x0(%r13),%r14
 f3: movq   $0x0,-0x48(%rbp)
 fb: mov    %rdx,0x0(%r14)
 ff: mov    0x0(%rbx),%rdi
103: movzbq 0x0(%rdi),%rsi
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
      af86ca4e