linux-kernel - Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in dbFindBits (2)

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Message-ID: <68d88c52.a00a0220.102ee.0021.GAE@google.com>
Date: Sat, 27 Sep 2025 18:16:02 -0700
From: syzbot <syzbot+9e90a1c5eedb9dc4c6cc@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, 
	xandfury@...il.com
Subject: Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in dbFindBits (2)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
UBSAN: shift-out-of-bounds in dbFindBits

ERROR: (device loop0): dbAllocBits: leaf page corrupt
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/jfs/jfs_dmap.c:3031:55
shift exponent 32 is too large for 32-bit type 'u32' (aka 'unsigned int')
CPU: 0 UID: 0 PID: 5831 Comm: syz.0.16 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
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
 dbFindBits+0xdf/0x1a0 fs/jfs/jfs_dmap.c:3031
 dbAllocDmapLev+0x16b/0x3c0 fs/jfs/jfs_dmap.c:1985
 dbAllocCtl+0x14a/0x9c0 fs/jfs/jfs_dmap.c:1825
 dbAllocAG+0x1e6/0xff0 fs/jfs/jfs_dmap.c:1353
 dbDiscardAG+0x2df/0x900 fs/jfs/jfs_dmap.c:1608
 jfs_ioc_trim+0x429/0x690 fs/jfs/jfs_discard.c:106
 jfs_ioctl+0x2b5/0x3d0 fs/jfs/ioctl.c:131
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:584
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f894198cda9
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:00007f894286c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f8941ba5fa0 RCX: 00007f894198cda9
RDX: 00000000200000c0 RSI: 00000000c0185879 RDI: 0000000000000004
RBP: 00007f8941a0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f8941ba5fa0 R15: 00007ffd6f2d8608
 </TASK>
---[ end trace ]---


Tested on:

commit:         51a24b7d Merge tag 'trace-tools-v6.17-rc5' of git://gi..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=103472e2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=231ef872e038778b
dashboard link: https://syzkaller.appspot.com/bug?extid=9e90a1c5eedb9dc4c6cc
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Note: no patches were applied.