gfs2: fix memory leaks in gfs2_fill_super error path

Fix two memory leaks in the gfs2_fill_super() error handling path when
transitioning a filesystem to read-write mode fails.

First leak: kthread objects (thread_struct, task_struct, etc.)
When gfs2_freeze_lock_shared() fails after init_threads() succeeds, the
created kernel threads (logd and quotad) are never destroyed. This
occurs because the fail_per_node label doesn't call
gfs2_destroy_threads().

Second leak: quota bitmap buffer (8192 bytes)
When gfs2_make_fs_rw() fails after gfs2_quota_init() succeeds but
before other operations complete, the allocated quota bitmap is never
freed.

The fix moves thread cleanup to the fail_per_node label to handle all
error paths uniformly. gfs2_destroy_threads() is safe to call
unconditionally as it checks for NULL pointers. Quota cleanup is added
in gfs2_make_fs_rw() to properly handle the withdrawal case where
quota initialization succeeds but the filesystem is then withdrawn.

Thread leak backtrace (gfs2_freeze_lock_shared failure):
  unreferenced object 0xffff88801d7bca80 (size 4480):
    copy_process+0x3a1/0x4670 kernel/fork.c:2422
    kernel_clone+0xf3/0x6e0 kernel/fork.c:2779
    kthread_create_on_node+0x100/0x150 kernel/kthread.c:478
    init_threads+0xab/0x350 fs/gfs2/ops_fstype.c:611
    gfs2_fill_super+0xe5c/0x1240 fs/gfs2/ops_fstype.c:1265

Quota leak backtrace (gfs2_make_fs_rw failure):
  unreferenced object 0xffff88812de7c000 (size 8192):
    gfs2_quota_init+0xe5/0x820 fs/gfs2/quota.c:1409
    gfs2_make_fs_rw+0x7a/0xe0 fs/gfs2/super.c:149
    gfs2_fill_super+0xfbb/0x1240 fs/gfs2/ops_fstype.c:1275

Reported-by: syzbot+aac438d7a1c44071e04b@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=aac438d7a1c44071e04b
Fixes: 6c7410f ("gfs2: gfs2_freeze_lock_shared cleanup")
Fixes: b66f723 ("gfs2: Improve gfs2_make_fs_rw error handling")
Link: https://lore.kernel.org/all/20260131062509.77974-1-kartikey406@gmail.com/T/ [v1]
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Author: deepanshu406

fs/gfs2/ops_fstype.c

@@ -1276,7 +1276,6 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc)
 
 	if (error) {
 		gfs2_freeze_unlock(sdp);
-		gfs2_destroy_threads(sdp);
 		fs_err(sdp, "can't make FS RW: %d\n", error);
 		goto fail_per_node;
 	}
@@ -1286,6 +1285,7 @@ static int gfs2_fill_super(struct super_block *sb, struct fs_context *fc)
 
 fail_per_node:
 	init_per_node(sdp, UNDO);
+	gfs2_destroy_threads(sdp);
 fail_inodes:
 	init_inodes(sdp, UNDO);
 fail_sb:

fs/gfs2/super.c

@@ -147,8 +147,10 @@ int gfs2_make_fs_rw(struct gfs2_sbd *sdp)
 	}
 
 	error = gfs2_quota_init(sdp);
-	if (!error && gfs2_withdrawn(sdp))
+	if (!error && gfs2_withdrawn(sdp)) {
+		gfs2_quota_cleanup(sdp);
 		error = -EIO;
+	}
 	if (!error)
 		set_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags);
 	return error;