[ashmem] Re: WARNING in __vm_enough_memory

Eric Biggers ebiggers at kernel.org
Wed Jun 12 19:30:09 UTC 2019


On Tue, Jan 16, 2018 at 06:20:37AM +0100, 'Dmitry Vyukov' via syzkaller-bugs wrote:
> On Tue, Jan 16, 2018 at 12:58 AM, syzbot
> <syzbot+cc298e15b6a571ba0c55 at syzkaller.appspotmail.com> wrote:
> > Hello,
> >
> > syzkaller hit the following crash on
> > 8418f88764046d0e8ca6a3c04a69a0e57189aa1e
> > git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
> > compiler: gcc (GCC) 7.1.1 20170620
> > .config is attached
> > Raw console output is attached.
> > C reproducer is attached
> > syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> > for information about syzkaller reproducers
> 
> 
> Most likely it is drivers/staging/android/ashmem.c which is guilty. So
> +ashmem maintainers.
> 
> 
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+cc298e15b6a571ba0c55 at syzkaller.appspotmail.com
> > It will help syzbot understand when the bug is fixed. See footer for
> > details.
> > If you forward the report, please keep this part and the footer.
> >
> > audit: type=1400 audit(1515720420.441:8): avc:  denied  { sys_admin } for
> > pid=3511 comm="syzkaller485245" capability=21
> > scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
> > tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns
> > permissive=1
> > audit: type=1400 audit(1515720420.495:9): avc:  denied  { sys_chroot } for
> > pid=3512 comm="syzkaller485245" capability=18
> > scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
> > tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns
> > permissive=1
> > ------------[ cut here ]------------
> > memory commitment underflow
> > WARNING: CPU: 0 PID: 3512 at mm/util.c:606 __vm_enough_memory+0x5a6/0x810
> > mm/util.c:604
> > Kernel panic - not syncing: panic_on_warn set ...
> >
> > CPU: 0 PID: 3512 Comm: syzkaller485245 Not tainted 4.15.0-rc7-next-20180111+
> > #94
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:17 [inline]
> >  dump_stack+0x194/0x257 lib/dump_stack.c:53
> >  panic+0x1e4/0x41c kernel/panic.c:183
> >  __warn+0x1dc/0x200 kernel/panic.c:547
> >  report_bug+0x211/0x2d0 lib/bug.c:184
> >  fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
> >  fixup_bug arch/x86/kernel/traps.c:247 [inline]
> >  do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
> >  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
> >  invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1102
> > RIP: 0010:__vm_enough_memory+0x5a6/0x810 mm/util.c:604
> > RSP: 0018:ffff8801bfbaf8e0 EFLAGS: 00010282
> > RAX: dffffc0000000008 RBX: 1ffff10037f75f21 RCX: ffffffff815a613e
> > RDX: 0000000000000000 RSI: 1ffff10037e84d3b RDI: 0000000000000293
> > RBP: ffff8801bfbafa90 R08: 1ffff10037f75eaf R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801bfbafa68
> > R13: ffffffff869b8c80 R14: 0000000000000fff R15: dffffc0000000000
> >  security_vm_enough_memory_mm+0x90/0xb0 security/security.c:327
> >  mmap_region+0x321/0x15a0 mm/mmap.c:1666
> >  do_mmap+0x73c/0xf70 mm/mmap.c:1494
> >  do_mmap_pgoff include/linux/mm.h:2224 [inline]
> >  vm_mmap_pgoff+0x1de/0x280 mm/util.c:333
> >  SYSC_mmap_pgoff mm/mmap.c:1544 [inline]
> >  SyS_mmap_pgoff+0x23b/0x5f0 mm/mmap.c:1502
> >  SYSC_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
> >  SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:91
> >  entry_SYSCALL_64_fastpath+0x29/0xa0
> > RIP: 0033:0x440ac9
> > RSP: 002b:00000000007dff58 EFLAGS: 00000212 ORIG_RAX: 0000000000000009
> > RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 0000000000440ac9
> > RDX: 0000000000000003 RSI: 0000000000fff000 RDI: 0000000020000000
> > RBP: 7fffffffffffffff R08: 00000000ffffffff R09: 0000000000000000
> > R10: 0000000000000032 R11: 0000000000000212 R12: 6873612f7665642f
> > R13: 6c616b7a79732f2e R14: 0000000000000000 R15: 0000000000000000
> > Dumping ftrace buffer:
> >    (ftrace buffer empty)
> > Kernel Offset: disabled
> > Rebooting in 86400 seconds..
> >
> >
> > ---
> > This bug is generated by a dumb bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for details.
> > Direct all questions to syzkaller at googlegroups.com.
> >
> > syzbot will keep track of this bug report.
> > If you forgot to add the Reported-by tag, once the fix for this bug is
> > merged
> > into any tree, please reply to this email with:
> > #syz fix: exact-commit-title
> > If you want to test a patch for this bug, please reply with:
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> > and provide the patch inline or as an attachment.
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> > Note: if the crash happens again, it will cause creation of a new bug
> > report.
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> >

Can the ashmem maintainers please look into this?  syzbot has continued to hit
this on more recent kernels too, e.g.
https://syzkaller.appspot.com/text?tag=CrashReport&x=13ba3d28a00000, where the
reproducer uses ASHMEM_SET_SIZE.

- Eric


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