[syzbot] [io-uring?] general protection fault in io_check_coalesce_buffer

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4ac65880ebca Add linux-next specific files for 20250904
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1290e312580000
kernel config: https://syzkaller.appspot.com/x/.config?x=fbc16d9faf3a88a4
dashboard link: https://syzkaller.appspot.com/bug?extid=3c84158e2daa468b2a3c
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=164f1a42580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1690e312580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/36645a51612c/disk-4ac65880.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bba80d634bef/vmlinux-4ac65880.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e58dd70dfd0f/bzImage-4ac65880.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3c8415...@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
CPU: 0 UID: 0 PID: 6175 Comm: syz.2.19 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:_compound_head include/linux/page-flags.h:284 [inline]
RIP: 0010:io_check_coalesce_buffer+0x354/0xb60 io_uring/rsrc.c:746
Code: f7 e8 e0 64 63 fd 4c 89 74 24 28 48 8b 44 24 18 4c 8b 74 d8 08 49 8d 6e 08 48 89 e8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 48 89 ef e8 ae 64 63 fd 48 8b 6d 00 48 89 ee 48
RSP: 0018:ffffc90003a5fa38 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 00000000000001ff RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff888024768ff8
RBP: 0000000000000008 R08: ffffea0001908007 R09: 1ffffd4000321000
R10: dffffc0000000000 R11: fffff94000321001 R12: ffff888024768ff8
R13: 0000000000000200 R14: 0000000000000000 R15: ffffea0001908000
FS: 00007fb6be5816c0(0000) GS:ffff8881259fa000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000095030 CR3: 0000000078fd4000 CR4: 00000000003526f0
Call Trace:
<TASK>
io_sqe_buffer_register+0x1ef/0x20a0 io_uring/rsrc.c:807
io_sqe_buffers_register+0x3b9/0x8e0 io_uring/rsrc.c:913
__io_uring_register io_uring/register.c:657 [inline]
__do_sys_io_uring_register io_uring/register.c:926 [inline]
__se_sys_io_uring_register+0xb85/0x11b0 io_uring/register.c:903
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: 0033:0x7fb6bd78ebe9
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:00007fb6be581038 EFLAGS: 00000246 ORIG_RAX: 00000000000001ab
RAX: ffffffffffffffda RBX: 00007fb6bd9c6180 RCX: 00007fb6bd78ebe9
RDX: 00002000000002c0 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00007fb6bd811e19 R08: 0000000000000000 R09: 0000000000000000
R10: 100000000000011a R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb6bd9c6218 R14: 00007fb6bd9c6180 R15: 00007ffdb92f0a28
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:_compound_head include/linux/page-flags.h:284 [inline]
RIP: 0010:io_check_coalesce_buffer+0x354/0xb60 io_uring/rsrc.c:746
Code: f7 e8 e0 64 63 fd 4c 89 74 24 28 48 8b 44 24 18 4c 8b 74 d8 08 49 8d 6e 08 48 89 e8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 48 89 ef e8 ae 64 63 fd 48 8b 6d 00 48 89 ee 48
RSP: 0018:ffffc90003a5fa38 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 00000000000001ff RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff888024768ff8
RBP: 0000000000000008 R08: ffffea0001908007 R09: 1ffffd4000321000
R10: dffffc0000000000 R11: fffff94000321001 R12: ffff888024768ff8
R13: 0000000000000200 R14: 0000000000000000 R15: ffffea0001908000
FS: 00007fb6be5816c0(0000) GS:ffff8881259fa000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000095030 CR3: 0000000078fd4000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
0: f7 e8 imul %eax
2: e0 64 loopne 0x68
4: 63 fd movsxd %ebp,%edi
6: 4c 89 74 24 28 mov %r14,0x28(%rsp)
b: 48 8b 44 24 18 mov 0x18(%rsp),%rax
10: 4c 8b 74 d8 08 mov 0x8(%rax,%rbx,8),%r14
15: 49 8d 6e 08 lea 0x8(%r14),%rbp
19: 48 89 e8 mov %rbp,%rax
1c: 48 c1 e8 03 shr $0x3,%rax
20: 48 b9 00 00 00 00 00 movabs $0xdffffc0000000000,%rcx
27: fc ff df
* 2a: 80 3c 08 00 cmpb $0x0,(%rax,%rcx,1) <-- trapping instruction
2e: 74 08 je 0x38
30: 48 89 ef mov %rbp,%rdi
33: e8 ae 64 63 fd call 0xfd6364e6
38: 48 8b 6d 00 mov 0x0(%rbp),%rbp
3c: 48 89 ee mov %rbp,%rsi
3f: 48 rex.W


---
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