Re: general protection fault in relay_switch_subbuf

[Andrew Morton]

(cc Jens ;))

On Thu, 21 Feb 2019 06:54:03 -0800 syzbot <syzbot+8e789999f280ccd6930f@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    c04e2a780caf Merge tag 'fsnotify_for_v5.0-rc4' of git://gi..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=133424c0c00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=505743eba4e4f68
> dashboard link: https://syzkaller.appspot.com/bug?extid=8e789999f280ccd6930f
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> 
> Unfortunately, I don't have any reproducer for this crash yet.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+8e789999f280ccd6930f@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 11600 Comm: syz-executor2 Not tainted 5.0.0-rc3+ #42
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> RIP: 0010:relay_switch_subbuf+0x27a/0xad0 kernel/relay.c:753
> Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 e2 07 00 00 48 b8 00 00 00 00  
> 00 fc ff df 48 8b 4b 58 48 8d 79 50 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
> 85 c9 07 00 00 48 ba 00 00 00 00 00 fc ff df 49 8b
> RSP: 0018:ffff88805e3ef790 EFLAGS: 00010206
> RAX: dffffc0000000000 RBX: ffff88804bc7db40 RCX: 0000000000000000
> RDX: 000000000000000a RSI: ffffffff8182d552 RDI: 0000000000000050
> RBP: ffff88805e3ef850 R08: ffff8880637f0600 R09: fffffbfff133b0b1
> R10: ffff88805e3ef850 R11: ffffffff899d8587 R12: 0000000000000000
> R13: ffff8880a7e05e00 R14: 0000000000000000 R15: 0000000000000000
> FS:  00007f1fdbddd700(0000) GS:ffff8880ae700000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000a50489 CR3: 00000000943a0000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   relay_flush kernel/relay.c:881 [inline]
>   relay_flush+0x1c4/0x280 kernel/relay.c:865
>   __blk_trace_startstop.isra.0+0x28b/0x8b0 kernel/trace/blktrace.c:668
>   blk_trace_ioctl+0x1c6/0x300 kernel/trace/blktrace.c:727
>   blkdev_ioctl+0x141/0x2120 block/ioctl.c:591
>   block_ioctl+0xee/0x130 fs/block_dev.c:1914
>   vfs_ioctl fs/ioctl.c:46 [inline]
>   file_ioctl fs/ioctl.c:509 [inline]
>   do_vfs_ioctl+0x107b/0x17d0 fs/ioctl.c:696
>   ksys_ioctl+0xab/0xd0 fs/ioctl.c:713
>   __do_sys_ioctl fs/ioctl.c:720 [inline]
>   __se_sys_ioctl fs/ioctl.c:718 [inline]
>   __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
>   do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x458099
> Code: 6d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7  
> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff  
> ff 0f 83 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007f1fdbddcc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458099
> RDX: 0000000000000000 RSI: 0000000000001275 RDI: 0000000000000005
> RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f1fdbddd6d4
> R13: 00000000004bf595 R14: 00000000004d0e88 R15: 00000000ffffffff
> Modules linked in:
> kobject: 'loop4' (000000005903bd4d): kobject_uevent_env
> kobject: 'loop4' (000000005903bd4d): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> ---[ end trace d4380d594e5099d1 ]---
> RIP: 0010:relay_switch_subbuf+0x27a/0xad0 kernel/relay.c:753
> Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 e2 07 00 00 48 b8 00 00 00 00  
> 00 fc ff df 48 8b 4b 58 48 8d 79 50 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f  
> 85 c9 07 00 00 48 ba 00 00 00 00 00 fc ff df 49 8b
> kobject: 'loop0' (0000000083b22ec7): kobject_uevent_env
> kobject: 'loop0' (0000000083b22ec7): fill_kobj_path: path  
> = '/devices/virtual/block/loop0'
> Unknown ioctl 19304
> kobject: 'loop3' (0000000050016e38): kobject_uevent_env
> RSP: 0018:ffff88805e3ef790 EFLAGS: 00010206
> kobject: 'loop3' (0000000050016e38): fill_kobj_path: path  
> = '/devices/virtual/block/loop3'
> RAX: dffffc0000000000 RBX: ffff88804bc7db40 RCX: 0000000000000000
> kobject: 'loop1' (000000002962ffee): kobject_uevent_env
> kobject: 'loop1' (000000002962ffee): fill_kobj_path: path  
> = '/devices/virtual/block/loop1'
> RDX: 000000000000000a RSI: ffffffff8182d552 RDI: 0000000000000050
> kobject: 'loop4' (000000005903bd4d): kobject_uevent_env
> kobject: 'loop4' (000000005903bd4d): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> RBP: ffff88805e3ef850 R08: ffff8880637f0600 R09: fffffbfff133b0b1
> kobject: 'loop4' (000000005903bd4d): kobject_uevent_env
> R10: ffff88805e3ef850 R11: ffffffff899d8587 R12: 0000000000000000
> kobject: 'loop4' (000000005903bd4d): fill_kobj_path: path  
> = '/devices/virtual/block/loop4'
> R13: ffff8880a7e05e00 R14: 0000000000000000 R15: 0000000000000000
> FS:  00007f1fdbddd700(0000) GS:ffff8880ae600000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000625208 CR3: 00000000943a0000 CR4: 00000000001406f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> 
> 
> ---
> 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@xxxxxxxxxxxxxxxxx
> 
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
> syzbot.