[Jfs-discussion] [syzbot] [jfs?] UBSAN: shift-out-of-bounds in dbJoin (2)

[syzbot <syz...@sy...>]

Hello,

syzbot found the following issue on:

HEAD commit:    4a26e7032d7d Merge tag 'core-bugs-2025-12-01' of git://git..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11ea9512580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dd808c444ce84c8
dashboard link: https://syzkaller.appspot.com/bug?extid=fa603ae6b02658401ca7
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=14dbe192580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=112d92b4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a40b77c72522/disk-4a26e703.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b2b4fa9b2036/vmlinux-4a26e703.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7105f0502b78/bzImage-4a26e703.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/1f7c2e37ce13/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=170ab512580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syz...@sy...

------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/jfs/jfs_dmap.c:2795:11
shift exponent 132 is too large for 32-bit type 'int'
CPU: 0 UID: 0 PID: 123 Comm: jfsCommit Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 ubsan_epilogue+0xa/0x40 lib/ubsan.c:233
 __ubsan_handle_shift_out_of_bounds+0x386/0x410 lib/ubsan.c:494
 dbJoin+0x2dc/0x300 fs/jfs/jfs_dmap.c:2795
 dbFreeBits+0x4e1/0xdb0 fs/jfs/jfs_dmap.c:2340
 dbFreeDmap fs/jfs/jfs_dmap.c:2089 [inline]
 dbFree+0x336/0x650 fs/jfs/jfs_dmap.c:398
 txFreeMap+0x7ff/0xde0 fs/jfs/jfs_txnmgr.c:2535
 txUpdateMap+0x308/0x9c0 fs/jfs/jfs_txnmgr.c:-1
 txLazyCommit fs/jfs/jfs_txnmgr.c:2665 [inline]
 jfs_lazycommit+0x3f1/0xa10 fs/jfs/jfs_txnmgr.c:2734
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x52d/0xa60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
---[ end trace ]---
Kernel panic - not syncing: UBSAN: panic_on_warn set ...
CPU: 0 UID: 0 PID: 123 Comm: jfsCommit Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x99/0x250 lib/dump_stack.c:120
 vpanic+0x237/0x6d0 kernel/panic.c:489
 panic+0xb9/0xc0 kernel/panic.c:626
 check_panic_on_warn+0x89/0xb0 kernel/panic.c:376
 __ubsan_handle_shift_out_of_bounds+0x386/0x410 lib/ubsan.c:494
 dbJoin+0x2dc/0x300 fs/jfs/jfs_dmap.c:2795
 dbFreeBits+0x4e1/0xdb0 fs/jfs/jfs_dmap.c:2340
 dbFreeDmap fs/jfs/jfs_dmap.c:2089 [inline]
 dbFree+0x336/0x650 fs/jfs/jfs_dmap.c:398
 txFreeMap+0x7ff/0xde0 fs/jfs/jfs_txnmgr.c:2535
 txUpdateMap+0x308/0x9c0 fs/jfs/jfs_txnmgr.c:-1
 txLazyCommit fs/jfs/jfs_txnmgr.c:2665 [inline]
 jfs_lazycommit+0x3f1/0xa10 fs/jfs/jfs_txnmgr.c:2734
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x52d/0xa60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Kernel Offset: disabled


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