linux-kernel - [syzbot] [gfs2?] UBSAN: shift-out-of-bounds in gfs2_dir

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Message-ID: <68754418.050a0220.33d347.000b.GAE@google.com>
Date: Mon, 14 Jul 2025 10:53:28 -0700
From: syzbot <syzbot+4708579bb230a0582a57@...kaller.appspotmail.com>
To: agruenba@...hat.com, gfs2@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [gfs2?] UBSAN: shift-out-of-bounds in gfs2_dir_read (2)

Hello,

syzbot found the following issue on:

HEAD commit:    347e9f5043c8 Linux 6.16-rc6
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13c070f0580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f62a2ef17395702a
dashboard link: https://syzkaller.appspot.com/bug?extid=4708579bb230a0582a57
compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-347e9f50.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/49ae91eb36e0/vmlinux-347e9f50.xz
kernel image: https://storage.googleapis.com/syzbot-assets/78497f74bd6b/bzImage-347e9f50.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4708579bb230a0582a57@...kaller.appspotmail.com

loop0: detected capacity change from 0 to 32768
gfs2: fsid=syz:syz: Trying to join cluster "lock_nolock", "syz:syz"
gfs2: fsid=syz:syz: Now mounting FS (format 1801)...
gfs2: fsid=syz:syz.s: journal 0 mapped with 5 extents in 0ms
gfs2: fsid=syz:syz.s: first mount done, others may mount
------------[ cut here ]------------
UBSAN: shift-out-of-bounds in fs/gfs2/dir.c:1544:15
shift exponent 32 is too large for 32-bit type 'u32' (aka 'unsigned int')
CPU: 0 UID: 0 PID: 5345 Comm: syz.0.0 Not tainted 6.16.0-rc6-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
 dir_e_read fs/gfs2/dir.c:1544 [inline]
 gfs2_dir_read+0x1730/0x1780 fs/gfs2/dir.c:1585
 gfs2_readdir+0x14c/0x1b0 fs/gfs2/file.c:116
 iterate_dir+0x5ac/0x770 fs/readdir.c:108
 __do_sys_getdents64 fs/readdir.c:410 [inline]
 __se_sys_getdents64+0xe4/0x260 fs/readdir.c:396
 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: 0033:0x7f97c858e929
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:00007f97c94ce038 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007f97c87b5fa0 RCX: 00007f97c858e929
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f97c8610b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f97c87b5fa0 R15: 00007ffd76387a88
 </TASK>
---[ end trace ]---


---
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