[syzbot] [btrfs?] WARNING in lookup_inline_extent_backref (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dbfc6422a34d Merge tag 'x86_urgent_for_v6.18_rc3' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11d993cd980000
kernel config: https://syzkaller.appspot.com/x/.config?x=25811b07889c90db
dashboard link: https://syzkaller.appspot.com/bug?extid=b0e66d3779134f468156
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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-dbfc6422.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/73c799811c6a/vmlinux-dbfc6422.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e1bb4619e00f/bzImage-dbfc6422.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b0e66d...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 5319 at fs/btrfs/extent-tree.c:836 lookup_inline_extent_backref+0x12c7/0x17f0 fs/btrfs/extent-tree.c:836
Modules linked in:
CPU: 0 UID: 0 PID: 5319 Comm: syz.0.0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:lookup_inline_extent_backref+0x12c7/0x17f0 fs/btrfs/extent-tree.c:836
Code: 05 fe 26 a5 0e 48 3b 84 24 e0 01 00 00 0f 85 8e 04 00 00 89 d8 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d e9 5b 4b 81 07 cc 90 <0f> 0b 90 48 8b 44 24 78 42 80 3c 30 00 74 0a 48 8b 7c 24 20 e8 90
RSP: 0000:ffffc9000d23e820 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 0000000000000001 RCX: 0000000000000000
RDX: ffff888000784900 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc9000d23ea48 R08: 0000000000000000 R09: 1ffffd40002891c8
R10: dffffc0000000000 R11: fffff940002891c9 R12: 1ffff1100a23a242
R13: 00000000000000b2 R14: dffffc0000000000 R15: ffff8880110e2000
FS: 00007f1616ed56c0(0000) GS:ffff88808d733000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7e2ed37000 CR3: 000000003f2e0000 CR4: 0000000000352ef0
Call Trace:
<TASK>
insert_inline_extent_backref+0xa8/0x2f0 fs/btrfs/extent-tree.c:1205
__btrfs_inc_extent_ref+0x263/0x9e0 fs/btrfs/extent-tree.c:1503
run_one_delayed_ref fs/btrfs/extent-tree.c:-1 [inline]
btrfs_run_delayed_refs_for_head fs/btrfs/extent-tree.c:1972 [inline]
__btrfs_run_delayed_refs+0xebd/0x4130 fs/btrfs/extent-tree.c:2047
btrfs_run_delayed_refs+0xe6/0x3b0 fs/btrfs/extent-tree.c:2159
btrfs_start_dirty_block_groups+0xd3d/0x10a0 fs/btrfs/block-group.c:3534
btrfs_commit_transaction+0x674/0x3950 fs/btrfs/transaction.c:2241
btrfs_sync_file+0xd30/0x1160 fs/btrfs/file.c:1818
generic_write_sync include/linux/fs.h:3046 [inline]
btrfs_do_write_iter+0x59a/0x710 fs/btrfs/file.c:1469
iter_file_splice_write+0x975/0x10e0 fs/splice.c:738
do_splice_from fs/splice.c:938 [inline]
direct_splice_actor+0x101/0x160 fs/splice.c:1161
splice_direct_to_actor+0x5a8/0xcc0 fs/splice.c:1105
do_splice_direct_actor fs/splice.c:1204 [inline]
do_splice_direct+0x181/0x270 fs/splice.c:1230
do_sendfile+0x4da/0x7e0 fs/read_write.c:1370
__do_sys_sendfile64 fs/read_write.c:1431 [inline]
__se_sys_sendfile64+0x13e/0x190 fs/read_write.c:1417
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: 0033:0x7f1615f8efc9
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:00007f1616ed5038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f16161e6090 RCX: 00007f1615f8efc9
RDX: 0000000000000000 RSI: 0000000000000007 RDI: 0000000000000008
RBP: 00007f1616011f91 R08: 0000000000000000 R09: 0000000000000000
R10: 000000007ffff000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f16161e6128 R14: 00007f16161e6090 R15: 00007fff32122a28
</TASK>


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[Qu Wenruo]

在 2025/10/27 19:35, syzbot 写道:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: dbfc6422a34d Merge tag 'x86_urgent_for_v6.18_rc3' of git:/..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=11d993cd980000
> kernel config: https://syzkaller.appspot.com/x/.config?x=25811b07889c90db
> dashboard link: https://syzkaller.appspot.com/bug?extid=b0e66d3779134f468156
> compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
>
> 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-dbfc6422.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/73c799811c6a/vmlinux-dbfc6422.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/e1bb4619e00f/bzImage-dbfc6422.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b0e66d...@syzkaller.appspotmail.com

This one is injecting an -ENOMEM at a critical path, which makes btrfs
to abort the current transaction.

To be honest, syzbot should not expect a completely quite system for
such injected error.

Thanks,
Qu