[syzbot] [bcachefs?] kernel BUG in bch2_bio_compress (3)

Hello,

syzbot found the following issue on:

HEAD commit:    5f33ebd2018c Merge tag 'drm-fixes-2025-07-26' of https://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15fa4034580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8adfe52da0de2761
dashboard link: https://syzkaller.appspot.com/bug?extid=1733f08e3b98628b164a
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

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-5f33ebd2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a554f67105dc/vmlinux-5f33ebd2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b3d52a10bce9/bzImage-5f33ebd2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

------------[ cut here ]------------
kernel BUG at fs/bcachefs/compress.c:525!
Oops: invalid opcode: 0000 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 5346 Comm: bch-copygc/loop Not tainted 6.16.0-rc7-syzkaller-00120-g5f33ebd2018c #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:__bio_compress fs/bcachefs/compress.c:525 [inline]
RIP: 0010:bch2_bio_compress+0x14b1/0x14c0 fs/bcachefs/compress.c:555
Code: fd 90 0f 0b e8 20 30 90 fd 90 0f 0b e8 18 30 90 fd 90 0f 0b e8 10 30 90 fd 90 0f 0b e8 08 30 90 fd 90 0f 0b e8 00 30 90 fd 90 <0f> 0b 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90
RSP: 0018:ffffc9000f51e600 EFLAGS: 00010293
RAX: ffffffff84300110 RBX: 0000000000000003 RCX: ffff88803d990000
RDX: 0000000000000000 RSI: 0000000000000800 RDI: 0000000000000000
RBP: ffffc9000f51e850 R08: 0000000000000005 R09: 0000000000000003
R10: ffffc90001a23033 R11: fffff52000344800 R12: 0000000000000800
R13: 0000000100000001 R14: 0000000000000000 R15: 0000000000002800
FS:  0000000000000000(0000) GS:ffff88808d218000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555e44a5168 CR3: 0000000011b80000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 bch2_write_extent fs/bcachefs/io_write.c:1060 [inline]
 __bch2_write+0xfb5/0x3900 fs/bcachefs/io_write.c:1554
 move_write fs/bcachefs/move.c:217 [inline]
 bch2_moving_ctxt_do_pending_writes+0x5a7/0xe60 fs/bcachefs/move.c:248
 bch2_move_ratelimit+0x8e8/0x1330 fs/bcachefs/move.c:585
 __bch2_move_data_phys+0x110f/0x1c50 fs/bcachefs/move.c:904
 bch2_evacuate_bucket+0x228/0x3a0 fs/bcachefs/move.c:1082
 bch2_copygc+0x3be3/0x4510 fs/bcachefs/movinggc.c:234
 bch2_copygc_thread+0x97a/0xe00 fs/bcachefs/movinggc.c:409
 kthread+0x711/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:__bio_compress fs/bcachefs/compress.c:525 [inline]
RIP: 0010:bch2_bio_compress+0x14b1/0x14c0 fs/bcachefs/compress.c:555
Code: fd 90 0f 0b e8 20 30 90 fd 90 0f 0b e8 18 30 90 fd 90 0f 0b e8 10 30 90 fd 90 0f 0b e8 08 30 90 fd 90 0f 0b e8 00 30 90 fd 90 <0f> 0b 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90
RSP: 0018:ffffc9000f51e600 EFLAGS: 00010293
RAX: ffffffff84300110 RBX: 0000000000000003 RCX: ffff88803d990000
RDX: 0000000000000000 RSI: 0000000000000800 RDI: 0000000000000000
RBP: ffffc9000f51e850 R08: 0000000000000005 R09: 0000000000000003
R10: ffffc90001a23033 R11: fffff52000344800 R12: 0000000000000800
R13: 0000000100000001 R14: 0000000000000000 R15: 0000000000002800


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