[syzbot] [io-uring?] general protection fault in io_uring_show_fdinfo (3)

[syzbot <syzbot+ea6ffa4864ebe64e7a04@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    aaa9c3550b60 Add linux-next specific files for 20251022
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=108bd734580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ad8f5526e5acd067
dashboard link: https://syzkaller.appspot.com/bug?extid=ea6ffa4864ebe64e7a04
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=176c9b04580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=173f7c58580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2fe0a8f92a64/disk-aaa9c355.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/199d2e804802/vmlinux-aaa9c355.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9371d55e359e/bzImage-aaa9c355.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ea6ffa4864ebe64e7a04@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 UID: 0 PID: 6013 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:__io_uring_show_fdinfo io_uring/fdinfo.c:103 [inline]
RIP: 0010:io_uring_show_fdinfo+0x371/0x1840 io_uring/fdinfo.c:255
Code: 0f 85 29 04 00 00 45 8b 36 44 89 f7 44 89 ee e8 15 3b 95 00 45 39 ee 76 11 e8 4b 39 95 00 45 89 fd 4c 8b 3c 24 e9 c9 03 00 00 <80> 3b 00 45 89 fd 0f 85 17 04 00 00 0f b6 2c 25 00 00 00 00 48 8b
RSP: 0018:ffffc90003a9f928 EFLAGS: 00010293
RAX: ffffffff812b443b RBX: dffffc0000000000 RCX: 0000000000000000
RDX: ffff88802ec55ac0 RSI: 0000000000000fff RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff88807aa560aa R09: 1ffff1100f54ac15
R10: dffffc0000000000 R11: ffffed100f54ac16 R12: 0000000000000008
R13: 0000000000000fff R14: 0000000000000000 R15: 0000000000000000
FS:  0000555561784500(0000) GS:ffff888125de4000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30263fff CR3: 000000007ad30000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 seq_show+0x5bc/0x730 fs/proc/fd.c:68
 seq_read_iter+0x4ef/0xe20 fs/seq_file.c:230
 seq_read+0x369/0x480 fs/seq_file.c:162
 vfs_read+0x200/0xa30 fs/read_write.c:570
 ksys_read+0x145/0x250 fs/read_write.c:715
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2bf498efc9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff1b261a48 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f2bf4be5fa0 RCX: 00007f2bf498efc9
RDX: 0000000000002020 RSI: 00002000000040c0 RDI: 0000000000000004
RBP: 00007f2bf4a11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2bf4be5fa0 R14: 00007f2bf4be5fa0 R15: 0000000000000003
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__io_uring_show_fdinfo io_uring/fdinfo.c:103 [inline]
RIP: 0010:io_uring_show_fdinfo+0x371/0x1840 io_uring/fdinfo.c:255
Code: 0f 85 29 04 00 00 45 8b 36 44 89 f7 44 89 ee e8 15 3b 95 00 45 39 ee 76 11 e8 4b 39 95 00 45 89 fd 4c 8b 3c 24 e9 c9 03 00 00 <80> 3b 00 45 89 fd 0f 85 17 04 00 00 0f b6 2c 25 00 00 00 00 48 8b
RSP: 0018:ffffc90003a9f928 EFLAGS: 00010293
RAX: ffffffff812b443b RBX: dffffc0000000000 RCX: 0000000000000000
RDX: ffff88802ec55ac0 RSI: 0000000000000fff RDI: 0000000000000000
RBP: 0000000000000000 R08: ffff88807aa560aa R09: 1ffff1100f54ac15
R10: dffffc0000000000 R11: ffffed100f54ac16 R12: 0000000000000008
R13: 0000000000000fff R14: 0000000000000000 R15: 0000000000000000
FS:  0000555561784500(0000) GS:ffff888125de4000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb550764e9c CR3: 000000007ad30000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	0f 85 29 04 00 00    	jne    0x42f
   6:	45 8b 36             	mov    (%r14),%r14d
   9:	44 89 f7             	mov    %r14d,%edi
   c:	44 89 ee             	mov    %r13d,%esi
   f:	e8 15 3b 95 00       	call   0x953b29
  14:	45 39 ee             	cmp    %r13d,%r14d
  17:	76 11                	jbe    0x2a
  19:	e8 4b 39 95 00       	call   0x953969
  1e:	45 89 fd             	mov    %r15d,%r13d
  21:	4c 8b 3c 24          	mov    (%rsp),%r15
  25:	e9 c9 03 00 00       	jmp    0x3f3
* 2a:	80 3b 00             	cmpb   $0x0,(%rbx) <-- trapping instruction
  2d:	45 89 fd             	mov    %r15d,%r13d
  30:	0f 85 17 04 00 00    	jne    0x44d
  36:	0f b6 2c 25 00 00 00 	movzbl 0x0,%ebp
  3d:	00
  3e:	48                   	rex.W
  3f:	8b                   	.byte 0x8b


---
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