[syzbot] [gfs2?] WARNING in rgblk_free (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 54e82e93ca93 Merge tag 'core_urgent_for_v6.19_rc4' of git:..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1216e5fa580000
kernel config: https://syzkaller.appspot.com/x/.config?x=513255d80ab78f2b
dashboard link: https://syzkaller.appspot.com/bug?extid=3e2c95229d1ab81a0bfd
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11b4bc3a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1015b922580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-54e82e93.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f3befb5f53a4/vmlinux-54e82e93.xz
kernel image: https://storage.googleapis.com/syzbot-assets/92820ca1dbd8/bzImage-54e82e93.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/074df7c33445/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=10da39fc580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3e2c95...@syzkaller.appspotmail.com

gfs2: fsid=syz:syz.0: first mount done, others may mount
gfs2: fsid=syz:syz.0: found 1 quota changes
------------[ cut here ]------------
WARNING: fs/gfs2/rgrp.c:2267 at rgblk_free+0x136/0x750 fs/gfs2/rgrp.c:2267, CPU#0: syz.0.17/5483
Modules linked in:
CPU: 0 UID: 0 PID: 5483 Comm: syz.0.17 Not tainted 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
RIP: 0010:rgblk_free+0x136/0x750 fs/gfs2/rgrp.c:2267
Code: c0 0f 85 fe 05 00 00 45 8b 36 44 89 f7 44 89 e6 e8 cf 42 b9 fd 45 39 e6 76 2e e8 05 41 b9 fd e9 89 00 00 00 e8 fb 40 b9 fd 90 <0f> 0b 65 48 8b 05 b0 f9 78 0e 48 3b 84 24 80 00 00 00 0f 85 a0 05
RSP: 0018:ffffc90002797a80 EFLAGS: 00010293
RAX: ffffffff8407c5a6 RBX: ffff88801fce7000 RCX: ffff888000634980
RDX: 0000000000000000 RSI: 0000000000000927 RDI: 0000000025540013
RBP: ffff88801fce7000 R08: ffffffff8f824677 R09: 1ffffffff1f048ce
R10: dffffc0000000000 R11: fffffbfff1f048cf R12: 0000000000000927
R13: 0000000000000001 R14: 0000000025540013 R15: dffffc0000000000
FS: 000055556242d500(0000) GS:ffff88808d414000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000011b5f000 CR4: 0000000000352ef0
Call Trace:
<TASK>
gfs2_unlink_di+0x296/0x420 fs/gfs2/rgrp.c:2566
gfs2_unlink_inode+0x11d/0x180 fs/gfs2/inode.c:1226
gfs2_unlink+0x448/0x550 fs/gfs2/inode.c:1298
vfs_rmdir+0x512/0x660 fs/namei.c:5236
do_rmdir+0x27f/0x4a0 fs/namei.c:5291
__do_sys_rmdir fs/namei.c:5315 [inline]
__se_sys_rmdir fs/namei.c:5313 [inline]
__x64_sys_rmdir+0x47/0x50 fs/namei.c:5313
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbfb358f7c9
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:00007ffc4142d868 EFLAGS: 00000246 ORIG_RAX: 0000000000000054
RAX: ffffffffffffffda RBX: 00007fbfb37e5fa0 RCX: 00007fbfb358f7c9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000100
RBP: 00007fbfb3613f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbfb37e5fa0 R14: 00007fbfb37e5fa0 R15: 0000000000000001
</TASK>


---
This report is generated by a bot. It may contain errors.
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If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

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.

If you want to overwrite report's subsystems, reply with:
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If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Andrew Price]

On 12/01/2026 15:49, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 54e82e93ca93 Merge tag 'core_urgent_for_v6.19_rc4' of git:..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1216e5fa580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=513255d80ab78f2b
> dashboard link: https://syzkaller.appspot.com/bug?extid=3e2c95229d1ab81a0bfd
> compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11b4bc3a580000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1015b922580000
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-54e82e93.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/f3befb5f53a4/vmlinux-54e82e93.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/92820ca1dbd8/bzImage-54e82e93.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/074df7c33445/mount_0.gz
> fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=10da39fc580000)
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+3e2c95...@syzkaller.appspotmail.com
>
> gfs2: fsid=syz:syz.0: first mount done, others may mount
> gfs2: fsid=syz:syz.0: found 1 quota changes
> ------------[ cut here ]------------
> WARNING: fs/gfs2/rgrp.c:2267 at rgblk_free+0x136/0x750 fs/gfs2/rgrp.c:2267, CPU#0: syz.0.17/5483

The test is scribbling on an rindex entry's ri_data0.

#syz test

--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -871,11 +871,15 @@ static int rgd_insert(struct gfs2_rgrpd *rgd)
rd_node);

parent = *newn;
- if (rgd->rd_addr < cur->rd_addr)
+ if (rgd->rd_addr < cur->rd_addr) {
+ if (rgd->rd_data0 + rgd->rd_data > cur->rd_addr)
+ return -EUCLEAN;
newn = &((*newn)->rb_left);
- else if (rgd->rd_addr > cur->rd_addr)
+ } else if (rgd->rd_addr > cur->rd_addr) {
+ if (rgd->rd_addr < cur->rd_data0)
+ return -EUCLEAN;
newn = &((*newn)->rb_right);
- else
+ } else
return -EEXIST;
}

@@ -944,7 +948,8 @@ static int read_rindex_entry(struct gfs2_inode *ip)
return 0;
}

- error = 0; /* someone else read in the rgrp; free it and ignore it */
+ if (error == -EEXIST)
+ error = 0; /* someone else read in the rgrp; free it and ignore it */
fail_glock:
gfs2_glock_put(rgd->rd_gl);

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+3e2c95...@syzkaller.appspotmail.com
Tested-by: syzbot+3e2c95...@syzkaller.appspotmail.com

Tested on:

commit: 0f61b186 Linux 6.19-rc5
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1030a99a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3027d9a5f96d82ca

dashboard link: https://syzkaller.appspot.com/bug?extid=3e2c95229d1ab81a0bfd
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=13a3e5fa580000

Note: testing is done by a robot and is best-effort only.