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

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Message-ID: <68d8ae8a.a00a0220.102ee.0025.GAE@google.com>
Date: Sat, 27 Sep 2025 20:42:02 -0700
From: syzbot <syzbot+13ba7f3e9a17f77250fe@...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 jfs_statfs (3)

Hello,

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

loop0: detected capacity change from 0 to 32768
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/jfs/super.c:140:14
shift exponent 115 is too large for 64-bit type 's64' (aka 'long long')
CPU: 0 UID: 0 PID: 6430 Comm: syz.0.16 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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
 jfs_statfs+0x4d1/0x550 fs/jfs/super.c:140
 statfs_by_dentry fs/statfs.c:66 [inline]
 vfs_statfs+0x144/0x2d0 fs/statfs.c:90
 ovl_check_namelen fs/overlayfs/super.c:387 [inline]
 ovl_lower_dir fs/overlayfs/super.c:403 [inline]
 ovl_get_lowerstack fs/overlayfs/super.c:1150 [inline]
 ovl_fill_super+0x9b8/0x35b0 fs/overlayfs/super.c:1416
 vfs_get_super fs/super.c:1325 [inline]
 get_tree_nodev+0xb8/0x150 fs/super.c:1344
 vfs_get_tree+0x8f/0x2b0 fs/super.c:1815
 do_new_mount+0x2a2/0x9e0 fs/namespace.c:3808
 do_mount fs/namespace.c:4136 [inline]
 __do_sys_mount fs/namespace.c:4347 [inline]
 __se_sys_mount+0x317/0x410 fs/namespace.c:4324
 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: 0033:0x7f8070b8e929
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:00007f80719a5038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f8070db5fa0 RCX: 00007f8070b8e929
RDX: 0000200000000000 RSI: 0000200000000140 RDI: 0000000000000000
RBP: 00007f8070c10b39 R08: 00002000000003c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f8070db5fa0 R15: 00007ffcaa757408
 </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=178192e2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=54ce6cac29609b49
dashboard link: https://syzkaller.appspot.com/bug?extid=13ba7f3e9a17f77250fe
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Note: no patches were applied.