Message-ID: <CACT4Y+Yqsq4eiyepwf=JGrWjpniub1nuEicT2F5WjDGCXkF1Zg@mail.gmail.com>
Date:   Thu, 7 Nov 2019 14:02:40 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+4e12d2d56f8ccc65c180@...kaller.appspotmail.com>
Cc:     Hans Verkuil <hverkuil@...all.nl>,
        LKML <linux-kernel@...r.kernel.org>, linux-media@...r.kernel.org,
        mchehab@...nel.org, sakari.ailus@...ux.intel.com,
        satendra.t@...sung.com,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Al Viro <viro@...iv.linux.org.uk>
Subject: Re: KASAN: use-after-free Write in __vb2_cleanup_fileio

On Mon, Oct 29, 2018 at 9:18 PM syzbot
<syzbot+4e12d2d56f8ccc65c180@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    9f51ae62c84a Merge git://git.kernel.org/pub/scm/linux/kern..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=130e0599400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=62118286bb772a24
> dashboard link: https://syzkaller.appspot.com/bug?extid=4e12d2d56f8ccc65c180
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1346e183400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=117c2713400000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+4e12d2d56f8ccc65c180@...kaller.appspotmail.com

Fix bisection says it was fixed by:

#syz fix: media: vb2: add waiting_in_dqbuf flag

So let's close the bug, so that it does not hang open on the media
subsystem, distracts people and prevents new bugs from being reported.

> ==================================================================
> BUG: KASAN: use-after-free in __vb2_cleanup_fileio+0x13d/0x160
> drivers/media/common/videobuf2/videobuf2-core.c:2318
> Write of size 4 at addr ffff8801d7730040 by task syz-executor965/5707
>
> CPU: 1 PID: 5707 Comm: syz-executor965 Not tainted 4.19.0+ #309
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x244/0x39d lib/dump_stack.c:113
>   print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
>   kasan_report_error mm/kasan/report.c:354 [inline]
>   kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
>   __asan_report_store4_noabort+0x17/0x20 mm/kasan/report.c:437
>   __vb2_cleanup_fileio+0x13d/0x160
> drivers/media/common/videobuf2/videobuf2-core.c:2318
>   vb2_core_queue_release+0x1e/0x80
> drivers/media/common/videobuf2/videobuf2-core.c:2043
>   vb2_queue_release drivers/media/common/videobuf2/videobuf2-v4l2.c:672
> [inline]
>   _vb2_fop_release+0x1d2/0x2b0
> drivers/media/common/videobuf2/videobuf2-v4l2.c:843
>   vb2_fop_release+0x77/0xc0
> drivers/media/common/videobuf2/videobuf2-v4l2.c:857
>   vivid_fop_release+0x18e/0x440 drivers/media/platform/vivid/vivid-core.c:474
>   v4l2_release+0xfb/0x1a0 drivers/media/v4l2-core/v4l2-dev.c:448
>   __fput+0x385/0xa30 fs/file_table.c:278
>   ____fput+0x15/0x20 fs/file_table.c:309
>   task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
>   tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>   exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
>   prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
>   syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
>   do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x400f30
> Code: 01 f0 ff ff 0f 83 b0 0a 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f
> 44 00 00 83 3d 9d 57 2d 00 00 75 14 b8 03 00 00 00 0f 05 <48> 3d 01 f0 ff
> ff 0f 83 84 0a 00 00 c3 48 83 ec 08 e8 3a 01 00 00
> RSP: 002b:00007ffd05f62478 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
> RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000400f30
> RDX: 0000000000000001 RSI: 0000000020000280 RDI: 0000000000000003
> RBP: 0000000000000000 R08: 00000000004002e0 R09: 00000000004002e0
> R10: 0000000000a73880 R11: 0000000000000246 R12: 0000000000401e40
> R13: 0000000000401ed0 R14: 0000000000000000 R15: 0000000000000000
>
> Allocated by task 5702:
>   save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>   set_track mm/kasan/kasan.c:460 [inline]
>   kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
>   kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
>   kmalloc include/linux/slab.h:546 [inline]
>   kzalloc include/linux/slab.h:741 [inline]
>   __vb2_init_fileio+0x1ce/0xc90
> drivers/media/common/videobuf2/videobuf2-core.c:2227
>   __vb2_perform_fileio+0xcfb/0x1210
> drivers/media/common/videobuf2/videobuf2-core.c:2361
>   vb2_read+0x3b/0x50 drivers/media/common/videobuf2/videobuf2-core.c:2493
>   vb2_fop_read+0x20a/0x400
> drivers/media/common/videobuf2/videobuf2-v4l2.c:898
>   v4l2_read+0x168/0x220 drivers/media/v4l2-core/v4l2-dev.c:317
>   do_loop_readv_writev fs/read_write.c:700 [inline]
>   do_iter_read+0x4a3/0x650 fs/read_write.c:924
>   vfs_readv+0x175/0x1c0 fs/read_write.c:986
>   do_readv+0x11a/0x310 fs/read_write.c:1019
>   __do_sys_readv fs/read_write.c:1106 [inline]
>   __se_sys_readv fs/read_write.c:1103 [inline]
>   __x64_sys_readv+0x75/0xb0 fs/read_write.c:1103
>   do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 5702:
>   save_stack+0x43/0xd0 mm/kasan/kasan.c:448
>   set_track mm/kasan/kasan.c:460 [inline]
>   __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
>   kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
>   __cache_free mm/slab.c:3498 [inline]
>   kfree+0xcf/0x230 mm/slab.c:3817
>   __vb2_cleanup_fileio+0xf8/0x160
> drivers/media/common/videobuf2/videobuf2-core.c:2320
>   vb2_core_queue_release+0x1e/0x80
> drivers/media/common/videobuf2/videobuf2-core.c:2043
>   vb2_queue_release drivers/media/common/videobuf2/videobuf2-v4l2.c:672
> [inline]
>   _vb2_fop_release+0x1d2/0x2b0
> drivers/media/common/videobuf2/videobuf2-v4l2.c:843
>   vb2_fop_release+0x77/0xc0
> drivers/media/common/videobuf2/videobuf2-v4l2.c:857
>   vivid_fop_release+0x18e/0x440 drivers/media/platform/vivid/vivid-core.c:474
>   v4l2_release+0xfb/0x1a0 drivers/media/v4l2-core/v4l2-dev.c:448
>   __fput+0x385/0xa30 fs/file_table.c:278
>   ____fput+0x15/0x20 fs/file_table.c:309
>   task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
>   tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>   exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166
>   prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
>   syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
>   do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> The buggy address belongs to the object at ffff8801d7730040
>   which belongs to the cache kmalloc-1k of size 1024
> The buggy address is located 0 bytes inside of
>   1024-byte region [ffff8801d7730040, ffff8801d7730440)
> The buggy address belongs to the page:
> page:ffffea00075dcc00 count:1 mapcount:0 mapping:ffff8801da800ac0 index:0x0
> compound_mapcount: 0
> flags: 0x2fffc0000010200(slab|head)
> raw: 02fffc0000010200 ffffea00075dcb88 ffffea00075dde08 ffff8801da800ac0
> raw: 0000000000000000 ffff8801d7730040 0000000100000007 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff8801d772ff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>   ffff8801d772ff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > ffff8801d7730000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>                                             ^
>   ffff8801d7730080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff8801d7730100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
> syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches
>
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