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

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Message-ID: <68754d09.a70a0220.5f69f.0001.GAE@google.com>
Date: Mon, 14 Jul 2025 11:31:37 -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: Re: [syzbot] [gfs2?] UBSAN: shift-out-of-bounds in gfs2_dir_read (2)

syzbot has found a reproducer for the following issue on:

HEAD commit:    347e9f5043c8 Linux 6.16-rc6
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11afb18c580000
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
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=172470f0580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16d0fd82580000

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
mounted in repro: https://storage.googleapis.com/syzbot-assets/2445b7dba270/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=15d7918c580000)

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

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: 5508 Comm: syz.0.16 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: 0033:0x7f9672d8e929
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:00007ffd2be2c848 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007f9672fb5fa0 RCX: 00007f9672d8e929
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f9672e10b39 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9672fb5fa0 R14: 00007f9672fb5fa0 R15: 0000000000000003
 </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.