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

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Message-ID: <68475c8a.050a0220.33aa0e.02e4.GAE@google.com>
Date: Mon, 09 Jun 2025 15:13:30 -0700
From: syzbot <syzbot+13ba7f3e9a17f77250fe@...kaller.appspotmail.com>
To: jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org, 
	shaggy@...nel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in jfs_statfs (3)

syzbot has found a reproducer for the following issue on:

HEAD commit:    475c850a7fdd Add linux-next specific files for 20250606
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=11fe2a82580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=28859360c84ac63d
dashboard link: https://syzkaller.appspot.com/bug?extid=13ba7f3e9a17f77250fe
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11c79a0c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=162aa9d4580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/2f1cf8485b7a/disk-475c850a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/976adb9f739e/vmlinux-475c850a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/0ac20b1308b7/bzImage-475c850a.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/fad6178a795b/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=122aa9d4580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+13ba7f3e9a17f77250fe@...kaller.appspotmail.com

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: 1 UID: 0 PID: 5841 Comm: syz-executor190 Not tainted 6.15.0-next-20250606-syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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:388 [inline]
 ovl_lower_dir fs/overlayfs/super.c:404 [inline]
 ovl_get_lowerstack fs/overlayfs/super.c:1150 [inline]
 ovl_fill_super+0x9d9/0x35d0 fs/overlayfs/super.c:1416
 vfs_get_super fs/super.c:1323 [inline]
 get_tree_nodev+0xbb/0x150 fs/super.c:1342
 vfs_get_tree+0x8f/0x2b0 fs/super.c:1802
 do_new_mount+0x24a/0xa40 fs/namespace.c:3874
 do_mount fs/namespace.c:4211 [inline]
 __do_sys_mount fs/namespace.c:4422 [inline]
 __se_sys_mount+0x317/0x410 fs/namespace.c:4399
 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: 0033:0x7f8347037a39
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 17 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffdd0158b28 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000200000000000 RCX: 00007f8347037a39
RDX: 0000200000000000 RSI: 0000200000000140 RDI: 0000000000000000
RBP: 00007f834708005e R08: 00002000000003c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0030656c69662f2e
R13: 65756e69746e6f63 R14: 633d73726f727265 R15: 0000000000000001
 </TASK>
---[ end trace ]---


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.