Message-ID: <CACT4Y+ZcXVrPAFrxfAohQ=PdqcN8fwrFq4ZGwzP-K_sSUEOY8A@mail.gmail.com>
Date:   Mon, 12 Feb 2018 16:57:55 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+a2a3c4909716e271487e@...kaller.appspotmail.com>
Cc:     linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com, Al Viro <viro@...iv.linux.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        arve@...roid.com, tkjos@...roid.com,
        Martijn Coenen <maco@...roid.com>, devel@...verdev.osuosl.org
Subject: Re: KASAN: use-after-free Read in remove_wait_queue

On Mon, Feb 12, 2018 at 4:54 PM, syzbot
<syzbot+a2a3c4909716e271487e@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot hit the following crash on upstream commit
> f1517df8701c9f12dae9ce7f43a5d300a6917619 (Thu Feb 8 23:18:32 2018 +0000)
> Merge tag 'nfsd-4.16' of git://linux-nfs.org/~bfields/linux
>
> So far this crash happened 3 times on upstream.
> C reproducer is attached.
> syzkaller reproducer is attached.
> Raw console output is attached.
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached.
> user-space arch: i386

This seems to be binder, so +binder maintainers.

> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+a2a3c4909716e271487e@...kaller.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.
>
> ==================================================================
> BUG: KASAN: use-after-free in debug_spin_lock_before
> kernel/locking/spinlock_debug.c:83 [inline]
> BUG: KASAN: use-after-free in do_raw_spin_lock+0x1e0/0x220
> kernel/locking/spinlock_debug.c:112
> Read of size 4 at addr ffff8801db1608a4 by task syzkaller818560/5118
>
> CPU: 1 PID: 5118 Comm: syzkaller818560 Not tainted 4.15.0+ #215
> 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
>  print_address_description+0x73/0x250 mm/kasan/report.c:256
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report+0x23b/0x360 mm/kasan/report.c:412
>  __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
>  debug_spin_lock_before kernel/locking/spinlock_debug.c:83 [inline]
>  do_raw_spin_lock+0x1e0/0x220 kernel/locking/spinlock_debug.c:112
>  __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:117 [inline]
>  _raw_spin_lock_irqsave+0x9e/0xc0 kernel/locking/spinlock.c:152
>  remove_wait_queue+0x81/0x350 kernel/sched/wait.c:50
>  ep_remove_wait_queue fs/eventpoll.c:595 [inline]
>  ep_unregister_pollwait.isra.7+0x18c/0x590 fs/eventpoll.c:613
>  ep_free+0x13f/0x320 fs/eventpoll.c:830
>  ep_eventpoll_release+0x44/0x60 fs/eventpoll.c:862
>  __fput+0x327/0x7e0 fs/file_table.c:209
>  ____fput+0x15/0x20 fs/file_table.c:243
>  task_work_run+0x199/0x270 kernel/task_work.c:113
>  tracehook_notify_resume include/linux/tracehook.h:191 [inline]
>  exit_to_usermode_loop+0x275/0x2f0 arch/x86/entry/common.c:166
>  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:265 [inline]
>  do_syscall_32_irqs_on arch/x86/entry/common.c:336 [inline]
>  do_fast_syscall_32+0xbe8/0xfa1 arch/x86/entry/common.c:392
>  entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
> RIP: 0023:0xf7f56c79
> RSP: 002b:00000000f7f3112c EFLAGS: 00000286 ORIG_RAX: 000000000000014a
> RAX: 0000000000000009 RBX: 0000000000000008 RCX: 0000000000000009
> RDX: 0000000000000000 RSI: 00000000000000f0 RDI: 0000000008120030
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>
> Allocated by task 5105:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>  set_track mm/kasan/kasan.c:459 [inline]
>  kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:552
>  kmem_cache_alloc_trace+0x136/0x740 mm/slab.c:3607
>  kmalloc include/linux/slab.h:512 [inline]
>  kzalloc include/linux/slab.h:701 [inline]
>  binder_get_thread+0x1cf/0x870 drivers/android/binder.c:4279
>  binder_poll+0x8c/0x390 drivers/android/binder.c:4393
>  ep_item_poll.isra.10+0xf2/0x320 fs/eventpoll.c:885
>  ep_insert+0x6a2/0x1ac0 fs/eventpoll.c:1457
>  SYSC_epoll_ctl fs/eventpoll.c:2104 [inline]
>  SyS_epoll_ctl+0x12bf/0x1a80 fs/eventpoll.c:1990
>  do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
>  do_fast_syscall_32+0x3ee/0xfa1 arch/x86/entry/common.c:392
>  entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
>
> Freed by task 5105:
>  save_stack+0x43/0xd0 mm/kasan/kasan.c:447
>  set_track mm/kasan/kasan.c:459 [inline]
>  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
>  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
>  __cache_free mm/slab.c:3485 [inline]
>  kfree+0xd9/0x260 mm/slab.c:3800
>  binder_free_thread drivers/android/binder.c:4306 [inline]
>  binder_thread_dec_tmpref+0x27f/0x310 drivers/android/binder.c:1879
>  binder_thread_release+0x4a1/0x6b0 drivers/android/binder.c:4382
>  binder_ioctl+0xc02/0x1417 drivers/android/binder.c:4599
>  C_SYSC_ioctl fs/compat_ioctl.c:1461 [inline]
>  compat_SyS_ioctl+0x151/0x2a30 fs/compat_ioctl.c:1407
>  do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
>  do_fast_syscall_32+0x3ee/0xfa1 arch/x86/entry/common.c:392
>  entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
>
> The buggy address belongs to the object at ffff8801db160800
>  which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 164 bytes inside of
>  512-byte region [ffff8801db160800, ffff8801db160a00)
> The buggy address belongs to the page:
> page:ffffea00076c5800 count:1 mapcount:0 mapping:ffff8801db160080 index:0x0
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffff8801db160080 0000000000000000 0000000100000006
> raw: ffffea00073c6ea0 ffffea0007076ce0 ffff8801db000940 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>  ffff8801db160780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff8801db160800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>
>> ffff8801db160880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>
>                                ^
>  ffff8801db160900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff8801db160980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
>
> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@...glegroups.com.
>
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