general protection fault in relay_switch_subbuf (3)

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: e472c64a Merge tag 'dmaengine-fix-5.4-rc6' of git://git.in..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14dc447ce00000
kernel config: https://syzkaller.appspot.com/x/.config?x=2bcb64e504d04eff
dashboard link: https://syzkaller.appspot.com/bug?extid=8a7381542c52b9d61a0c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
CC: [gre...@linuxfoundation.org ja...@google.com
linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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+8a7381...@syzkaller.appspotmail.com

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 28948 Comm: syz-executor.2 Not tainted 5.4.0-rc5+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:relay_switch_subbuf+0x216/0x920 kernel/relay.c:755
Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 bc 06 00 00 48 b8 00 00 00 00
00 fc ff df 4c 8b 7b 58 49 8d 7f 50 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f
85 7d 06 00 00 48 ba 00 00 00 00 00 fc ff df 49 8b
RSP: 0018:ffff88804ad37990 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff8880904a6040 RCX: ffffc9000a37f000
RDX: 000000000000000a RSI: ffffffff8173d3de RDI: 0000000000000050
RBP: ffff88804ad379e8 R08: ffff888098fee200 R09: fffffbfff11fc409
R10: ffff88804ad379e8 R11: ffffffff88fe2047 R12: 0000000000000000
R13: 0000000000000000 R14: ffff888099074800 R15: 0000000000000000
FS: 00007f5212dae700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f442abb0518 CR3: 00000000a0f60000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
relay_flush kernel/relay.c:883 [inline]
relay_flush+0x1c4/0x280 kernel/relay.c:867
__blk_trace_startstop.isra.0+0x216/0x630 kernel/trace/blktrace.c:662
blk_trace_ioctl+0x1c6/0x300 kernel/trace/blktrace.c:722
blkdev_ioctl+0x126/0x1c20 block/ioctl.c:592
block_ioctl+0xee/0x130 fs/block_dev.c:1954
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0xdb6/0x13e0 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+0xfa/0x760 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459f49
Code: ad b6 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f5212dadc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459f49
RDX: 0000000000000000 RSI: 0000000000001275 RDI: 0000000000000004
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f5212dae6d4
R13: 00000000004c1801 R14: 00000000004d52a8 R15: 00000000ffffffff
Modules linked in:
---[ end trace 293341f9fae13bfb ]---
RIP: 0010:relay_switch_subbuf+0x216/0x920 kernel/relay.c:755
Code: 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 bc 06 00 00 48 b8 00 00 00 00
00 fc ff df 4c 8b 7b 58 49 8d 7f 50 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f
85 7d 06 00 00 48 ba 00 00 00 00 00 fc ff df 49 8b
RSP: 0018:ffff88804ad37990 EFLAGS: 00010206
RAX: dffffc0000000000 RBX: ffff8880904a6040 RCX: ffffc9000a37f000
RDX: 000000000000000a RSI: ffffffff8173d3de RDI: 0000000000000050
RBP: ffff88804ad379e8 R08: ffff888098fee200 R09: fffffbfff11fc409
R10: ffff88804ad379e8 R11: ffffffff88fe2047 R12: 0000000000000000
R13: 0000000000000000 R14: ffff888099074800 R15: 0000000000000000
FS: 00007f5212dae700(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 00000000a0f60000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.