Re: [syzbot] general protection fault in __io_queue_sqe

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    b9011c7e671d Add linux-next specific files for 20210816
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1784d5e9300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a245d1aa4f055cc1
dashboard link: https://syzkaller.appspot.com/bug?extid=2b85e9379c34945fe38f
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17479216300000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=147f0111300000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2b85e9379c34945fe38f@xxxxxxxxxxxxxxxxxxxxxxxxx

general protection fault, probably for non-canonical address 0xdffffc000000000b: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000058-0x000000000000005f]
CPU: 0 PID: 6542 Comm: syz-executor423 Not tainted 5.14.0-rc5-next-20210816-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:__io_req_set_refcount fs/io_uring.c:1152 [inline]
RIP: 0010:__io_prep_linked_timeout fs/io_uring.c:1348 [inline]
RIP: 0010:io_prep_linked_timeout fs/io_uring.c:1356 [inline]
RIP: 0010:__io_queue_sqe+0x278/0xeb0 fs/io_uring.c:6708
Code: 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 07 0c 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 65 70 49 8d 7c 24 58 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 3e 0b 00 00 45 8b 74 24 58 31
RSP: 0018:ffffc90002e4fd48 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 1ffff920005c9fb0 RCX: 0000000000000000
RDX: 000000000000000b RSI: ffffffff81e1bcbf RDI: 0000000000000058
RBP: ffff88807afc6280 R08: 0000000000000001 R09: ffff88807afc62df
R10: ffffed100f5f8c5b R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff88807afc62f0 R15: ffff88807afc62f0
FS:  000000000169a300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200002c4 CR3: 0000000072b0d000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 io_req_task_submit+0xaa/0x120 fs/io_uring.c:2139
 tctx_task_work+0x106/0x540 fs/io_uring.c:2063
 task_work_run+0xdd/0x1a0 kernel/task_work.c:164
 tracehook_notify_signal include/linux/tracehook.h:212 [inline]
 handle_signal_work kernel/entry/common.c:146 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
 exit_to_user_mode_prepare+0x256/0x290 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x43f169
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 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 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe2bd862a8 EFLAGS: 00000246 ORIG_RAX: 00000000000001aa
RAX: 0000000000000200 RBX: 00000000004ad018 RCX: 000000000043f169
RDX: 0000000000000000 RSI: 00000000000045f5 RDI: 0000000000000003
RBP: 0000000000403150 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004031e0
R13: 0000000000000000 R14: 00000000004ad018 R15: 0000000000400488
Modules linked in:
---[ end trace bbf4e48f02e6cc2c ]---
RIP: 0010:__io_req_set_refcount fs/io_uring.c:1152 [inline]
RIP: 0010:__io_prep_linked_timeout fs/io_uring.c:1348 [inline]
RIP: 0010:io_prep_linked_timeout fs/io_uring.c:1356 [inline]
RIP: 0010:__io_queue_sqe+0x278/0xeb0 fs/io_uring.c:6708
Code: 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 07 0c 00 00 48 b8 00 00 00 00 00 fc ff df 4c 8b 65 70 49 8d 7c 24 58 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 3e 0b 00 00 45 8b 74 24 58 31
RSP: 0018:ffffc90002e4fd48 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 1ffff920005c9fb0 RCX: 0000000000000000
RDX: 000000000000000b RSI: ffffffff81e1bcbf RDI: 0000000000000058
RBP: ffff88807afc6280 R08: 0000000000000001 R09: ffff88807afc62df
R10: ffffed100f5f8c5b R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: ffff88807afc62f0 R15: ffff88807afc62f0
FS:  000000000169a300(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200002c4 CR3: 0000000072b0d000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
   0:	89 fa                	mov    %edi,%edx
   2:	48 c1 ea 03          	shr    $0x3,%rdx
   6:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
   a:	0f 85 07 0c 00 00    	jne    0xc17
  10:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
  17:	fc ff df 
  1a:	4c 8b 65 70          	mov    0x70(%rbp),%r12
  1e:	49 8d 7c 24 58       	lea    0x58(%r12),%rdi
  23:	48 89 fa             	mov    %rdi,%rdx
  26:	48 c1 ea 03          	shr    $0x3,%rdx
  2a:	0f b6 04 02          	movzbl (%rdx,%rax,1),%eax <-- trapping instruction
  2e:	84 c0                	test   %al,%al
  30:	74 08                	je     0x3a
  32:	3c 03                	cmp    $0x3,%al
  34:	0f 8e 3e 0b 00 00    	jle    0xb78
  3a:	45 8b 74 24 58       	mov    0x58(%r12),%r14d
  3f:	31                   	.byte 0x31