[syzbot] [netfs?] general protection fault in netfs_put_subrequest

syzbot
2026-04-14T13:58:30Z

Hello,

syzbot found the following issue on:

HEAD commit: 9a9c8ce300cd Merge tag 'kbuild-fixes-7.0-4' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=142de106580000
kernel config: https://syzkaller.appspot.com/x/.config?x=5a3e5e8c17cc174e
dashboard link: https://syzkaller.appspot.com/bug?extid=a0788ffdca16ee21c493
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-9a9c8ce3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/073107a6c46a/vmlinux-9a9c8ce3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f6457493483c/bzImage-9a9c8ce3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a0788ffdca16ee21c493@syzkaller.appspotmail.com

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000055: 0000 [#1] SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x00000000000002a8-0x00000000000002af]
CPU: 1 UID: 0 PID: 1247 Comm: kworker/u32:10 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Workqueue: events_unbound netfs_unbuffered_write_async

RIP: 0010:netfs_put_subrequest+0x88/0x4e0 fs/netfs/objects.c:248
Code: df 48 c1 ea 03 80 3c 02 00 0f 85 fa 03 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 2b 48 8d bd ac 02 00 00 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 96
RSP: 0018:ffffc9000619fa48 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff88804679adc0 RCX: 0000000000000000
RDX: 0000000000000055 RSI: 0000000000000008 RDI: 00000000000002ac
RBP: 0000000000000000 R08: 1ffff110055b509b R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000007
R13: 0000000000000001 R14: 0000000000000002 R15: ffff88804679ae10
FS: 0000000000000000(0000) GS:ffff8880d6438000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000002b072000 CR4: 0000000000352ef0
Call Trace:
<TASK>
netfs_clear_subrequests+0x158/0x260 fs/netfs/objects.c:106
netfs_unbuffered_write_done fs/netfs/direct_write.c:59 [inline]
netfs_unbuffered_write+0x13ac/0x2260 fs/netfs/direct_write.c:202
netfs_unbuffered_write_async+0x19/0x30 fs/netfs/direct_write.c:211
process_one_work+0xa23/0x19a0 kernel/workqueue.c:3276
process_scheduled_works kernel/workqueue.c:3359 [inline]
worker_thread+0x5ef/0xe50 kernel/workqueue.c:3440
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x754/0xd80 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:netfs_put_subrequest+0x88/0x4e0 fs/netfs/objects.c:248
Code: df 48 c1 ea 03 80 3c 02 00 0f 85 fa 03 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 2b 48 8d bd ac 02 00 00 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48 89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 96
RSP: 0018:ffffc9000619fa48 EFLAGS: 00010207
RAX: dffffc0000000000 RBX: ffff88804679adc0 RCX: 0000000000000000
RDX: 0000000000000055 RSI: 0000000000000008 RDI: 00000000000002ac
RBP: 0000000000000000 R08: 1ffff110055b509b R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000007
R13: 0000000000000001 R14: 0000000000000002 R15: ffff88804679ae10
FS: 0000000000000000(0000) GS:ffff8880d6438000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000031877000 CR4: 0000000000352ef0
----------------
Code disassembly (best guess), 1 bytes skipped:
0: 48 c1 ea 03 shr $0x3,%rdx
4: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
8: 0f 85 fa 03 00 00 jne 0x408
e: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
15: fc ff df
18: 48 8b 2b mov (%rbx),%rbp
1b: 48 8d bd ac 02 00 00 lea 0x2ac(%rbp),%rdi
22: 48 89 fa mov %rdi,%rdx
25: 48 c1 ea 03 shr $0x3,%rdx
* 29: 0f b6 14 02 movzbl (%rdx,%rax,1),%edx <-- trapping instruction
2d: 48 89 f8 mov %rdi,%rax
30: 83 e0 07 and $0x7,%eax
33: 83 c0 03 add $0x3,%eax
36: 38 d0 cmp %dl,%al
38: 7c 08 jl 0x42
3a: 84 d2 test %dl,%dl
3c: 0f .byte 0xf
3d: 85 .byte 0x85
3e: 96 xchg %eax,%esi

---
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