[syzbot] [gfs2?] WARNING in gfs2_fill_super

[syzbot] [gfs2?] WARNING in gfs2_fill_super

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    09c0f7f1bcdb Add linux-next specific files for 20260323
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=142ade02580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c0c30527ccbcb0f2
dashboard link: https://syzkaller.appspot.com/bug?extid=b441db1854c360b83221
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=145e16da580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16b33b52580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c320a7a1bc69/disk-09c0f7f1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4a5b231960d2/vmlinux-09c0f7f1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8e2b84b9674d/bzImage-09c0f7f1.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/a4941369e2d2/mount_0.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=170daa06580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b441db1854c360b83221@syzkaller.appspotmail.com

loop4: detected capacity change from 0 to 32768
------------[ cut here ]------------
kmem_cache of name 'gfs2-bufdata/syz:syz' already exists
WARNING: mm/slab_common.c:112 at kmem_cache_sanity_check mm/slab_common.c:111 [inline], CPU#1: syz.4.21/6090
WARNING: mm/slab_common.c:112 at __kmem_cache_create_args+0xac/0x440 mm/slab_common.c:352, CPU#1: syz.4.21/6090
Modules linked in:
CPU: 1 UID: 0 PID: 6090 Comm: syz.4.21 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:kmem_cache_sanity_check mm/slab_common.c:111 [inline]
RIP: 0010:__kmem_cache_create_args+0xaf/0x440 mm/slab_common.c:352
Code: 86 8e 4d 8b 24 24 49 81 fc 18 68 86 8e 74 20 49 8b 7c 24 f8 48 89 de e8 3f 5c 9c 09 85 c0 75 e2 48 8d 3d 54 70 06 0e 48 89 de <67> 48 0f b9 3a 48 89 df be 20 00 00 00 e8 df 5d 9c 09 48 85 c0 0f
RSP: 0018:ffffc900025f7948 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88807ac1dac0 RCX: 0000000000000005
RDX: 000000007ac1da04 RSI: ffff88807ac1dac0 RDI: ffffffff9016e0b0
RBP: 0000000000000000 R08: ffffffff901246f7 R09: 1ffffffff20248de
R10: dffffc0000000000 R11: fffffbfff20248df R12: ffff8881442f37e0
R13: ffff88807caa0000 R14: 0000000000000050 R15: ffffc900025f7a60
FS:  000055555c597500(0000) GS:ffff888125548000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fefd604b544 CR3: 0000000035aa2000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __kmem_cache_create include/linux/slab.h:390 [inline]
 gfs2_fill_super+0x13a4/0x21d0 fs/gfs2/ops_fstype.c:1202
 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694
 gfs2_get_tree+0x51/0x1e0 fs/gfs2/ops_fstype.c:1342
 vfs_get_tree+0x92/0x2a0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3764 [inline]
 do_new_mount+0x341/0xd30 fs/namespace.c:3840
 do_mount fs/namespace.c:4173 [inline]
 __do_sys_mount fs/namespace.c:4372 [inline]
 __se_sys_mount+0x31d/0x420 fs/namespace.c:4349
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fefd5f9da0a
Code: 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff558aaf78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fff558ab000 RCX: 00007fefd5f9da0a
RDX: 00002000000124c0 RSI: 0000200000012500 RDI: 00007fff558aafc0
RBP: 00002000000124c0 R08: 00007fff558ab000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000200000012500
R13: 00007fff558aafc0 R14: 00000000000125c7 R15: 0000200000000180
 </TASK>
----------------
Code disassembly (best guess):
   0:	86 8e 4d 8b 24 24    	xchg   %cl,0x24248b4d(%rsi)
   6:	49 81 fc 18 68 86 8e 	cmp    $0xffffffff8e866818,%r12
   d:	74 20                	je     0x2f
   f:	49 8b 7c 24 f8       	mov    -0x8(%r12),%rdi
  14:	48 89 de             	mov    %rbx,%rsi
  17:	e8 3f 5c 9c 09       	call   0x99c5c5b
  1c:	85 c0                	test   %eax,%eax
  1e:	75 e2                	jne    0x2
  20:	48 8d 3d 54 70 06 0e 	lea    0xe067054(%rip),%rdi        # 0xe06707b
  27:	48 89 de             	mov    %rbx,%rsi
* 2a:	67 48 0f b9 3a       	ud1    (%edx),%rdi <-- trapping instruction
  2f:	48 89 df             	mov    %rbx,%rdi
  32:	be 20 00 00 00       	mov    $0x20,%esi
  37:	e8 df 5d 9c 09       	call   0x99c5e1b
  3c:	48 85 c0             	test   %rax,%rax
  3f:	0f                   	.byte 0xf


---
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Forwarded: [PATCH] gfs2: fix missing kmem_cache_destroy() of sd_bufdata in gfs2_kill_sb()

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: [PATCH] gfs2: fix missing kmem_cache_destroy() of sd_bufdata in gfs2_kill_sb()
Author: kartikey406@gmail.com

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


gfs2_fill_super() creates a per-superblock slab cache for gfs2_bufdata
objects with a name derived from the filesystem name:

  sdp->sd_bufdata = kmem_cache_create("gfs2-bufdata/<fsname>", ...);

However, gfs2_kill_sb() does not call kmem_cache_destroy() on this
cache during unmount. This means the cache persists after the filesystem
is unmounted, and a subsequent mount attempt will try to create a cache
with the same name, triggering a warning in kmem_cache_sanity_check():

  kmem_cache of name 'gfs2-bufdata/syz:syz' already exists
  WARNING: mm/slab_common.c:112

The error path in gfs2_fill_super() already handles this correctly via
the fail_bufdata label. Add the missing kmem_cache_destroy() call to
gfs2_kill_sb() to fix the leak on the normal unmount path.

Reported-by: syzbot+b441db1854c360b83221@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b441db1854c360b83221
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 fs/gfs2/ops_fstype.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index b44adb40635d..38e4a9dc96bc 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1803,7 +1803,7 @@ static void gfs2_kill_sb(struct super_block *sb)
 	set_bit(SDF_KILL, &sdp->sd_flags);
 	gfs2_flush_delete_work(sdp);
 	destroy_workqueue(sdp->sd_delete_wq);
-
+	kmem_cache_destroy(sdp->sd_bufdata);
 	kill_block_super(sb);
 }
 
-- 
2.43.0

Forwarded: [PATCH] gfs2: fix duplicate kmem_cache name on concurrent mounts

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: [PATCH] gfs2: fix duplicate kmem_cache name on concurrent mounts
Author: kartikey406@gmail.com

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

When gfs2_fill_super() creates the per-filesystem bufdata cache, it
uses sd_fsname as part of the cache name:

  sdp->sd_bufdata = kmem_cache_create("gfs2-bufdata/<fsname>", ...);

At this point sd_fsname is set from sd_table_name (e.g. "syz:syz"),
which is the same for all concurrent mounts of the same device.
The unique suffix (.s for spectator, .N for journal ID) is only
added to sd_fsname AFTER wait_on_journal() completes, since the
journal ID is assigned by the locking subsystem during mount.

With multiple concurrent mounts of the same device (as triggered by
syzkaller with procs:5), multiple calls to gfs2_fill_super() all try
to create a cache named "gfs2-bufdata/syz:syz" before any of them
reaches the point where sd_fsname becomes unique, triggering:

  kmem_cache of name 'gfs2-bufdata/syz:syz' already exists
  WARNING: mm/slab_common.c:112

Fix this by moving the bufdata cache creation to after
wait_on_journal() completes and sd_fsname has been updated with its
unique suffix. Also move the fail_bufdata cleanup label accordingly
in the error unwind path.

Reported-by: syzbot+b441db1854c360b83221@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=b441db1854c360b83221
Fixes: 767e4de3ffce ("gfs2: per-filesystem bufdata cache")
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 fs/gfs2/ops_fstype.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index b44adb40635d..7f8e04c11494 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1198,17 +1198,9 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc)
 	if (!sdp->sd_delete_wq)
 		goto fail_glock_wq;
 
-	char *bufdata_name = kasprintf(GFP_KERNEL, "gfs2-bufdata/%s", sdp->sd_fsname);
-	sdp->sd_bufdata = kmem_cache_create(bufdata_name,
-					    sizeof(struct gfs2_bufdata),
-					    0, 0, NULL);
-	kfree(bufdata_name);
-	if (!sdp->sd_bufdata)
-		goto fail_delete_wq;
-
 	error = gfs2_sys_fs_add(sdp);
 	if (error)
-		goto fail_bufdata;
+		goto fail_delete_wq;
 
 	gfs2_create_debugfs_file(sdp);
 
@@ -1255,6 +1247,14 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc)
 		snprintf(sdp->sd_fsname, sizeof(sdp->sd_fsname), "%s.%u",
 			 sdp->sd_table_name, sdp->sd_lockstruct.ls_jid);
 
+	char *bufdata_name = kasprintf(GFP_KERNEL, "gfs2-bufdata/%s", sdp->sd_fsname);
+	sdp->sd_bufdata = kmem_cache_create(bufdata_name,
+			                    sizeof(struct gfs2_bufdata),
+                                             0, 0, NULL);
+	kfree(bufdata_name);
+	if (!sdp->sd_bufdata)
+		goto fail_sb;
+
 	error = init_inodes(sdp, DO);
 	if (error)
 		goto fail_sb;
@@ -1304,6 +1304,7 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc)
 	if (sb->s_root)
 		dput(sb->s_root);
 	sb->s_root = NULL;
+	kmem_cache_destroy(sdp->sd_bufdata);
 fail_locking:
 	init_locking(sdp, &mount_gh, UNDO);
 fail_lm:
@@ -1313,8 +1314,6 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc)
 fail_debug:
 	gfs2_delete_debugfs_file(sdp);
 	gfs2_sys_fs_del(sdp);
-fail_bufdata:
-	kmem_cache_destroy(sdp->sd_bufdata);
 fail_delete_wq:
 	destroy_workqueue(sdp->sd_delete_wq);
 fail_glock_wq:
-- 
2.43.0