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

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Message-ID: <68d8b1d2.050a0220.25d7ab.0468.GAE@google.com>
Date: Sat, 27 Sep 2025 20:56:02 -0700
From: syzbot <syzbot+5ad0824204c7bf9b67f2@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com, 
	xandfury@...il.com
Subject: Re: [syzbot] [fs?] UBSAN: shift-out-of-bounds in minix_statfs

Hello,

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

loop0: detected capacity change from 0 to 64
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/minix/inode.c:399:57
shift exponent 768 is too large for 64-bit type 'unsigned long'
CPU: 1 UID: 0 PID: 6533 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
 minix_statfs+0x31c/0x340 fs/minix/inode.c:399
 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_get_upper fs/overlayfs/super.c:505 [inline]
 ovl_fill_super+0x767/0x35b0 fs/overlayfs/super.c:1392
 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: 0033:0x7f895c78d169
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:00007f895b9fe038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007f895c9a5fa0 RCX: 00007f895c78d169
RDX: 0000400000000000 RSI: 0000400000000080 RDI: 0000000000000000
RBP: 00007f895c80e2a0 R08: 00004000000002c0 R09: 0000000000000000
R10: 0000000000010000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f895c9a5fa0 R15: 00007ffffbd08258
 </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=112e72e2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5376b4bed9a84961
dashboard link: https://syzkaller.appspot.com/bug?extid=5ad0824204c7bf9b67f2
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Note: no patches were applied.