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

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Message-ID: <68d8aa11.050a0220.25d7ab.045e.GAE@google.com>
Date: Sat, 27 Sep 2025 20:22:57 -0700
From: syzbot <syzbot+13ba7f3e9a17f77250fe@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Forwarded: Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in
 jfs_statfs (3)

For archival purposes, forwarding an incoming command email to
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***

Subject: Re: [syzbot] [jfs?] UBSAN: shift-out-of-bounds in jfs_statfs (3)
Author: xandfury@...il.com

syzbot <syzbot+13ba7f3e9a17f77250fe@...kaller.appspotmail.com> writes:

> 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.

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master