erofs: fix metabuf leak in inode xattr initialization

commit bb88e8d ("erofs: use meta buffers for xattr operations")
converted xattr operations to use on-stack erofs_buf instances.
erofs_init_inode_xattrs() uses such a metabuf while reading the inline
xattr header and shared xattr id array.

Some error paths after erofs_read_metabuf() leave through out_unlock
without dropping the metabuf, so the folio reference can leak.

Consolidate the cleanup at out_unlock. erofs_put_metabuf() is a
no-op if no folio has been acquired, and this keeps all paths after
taking EROFS_I_BL_XATTR_BIT covered by a single cleanup site.

Fixes: bb88e8d ("erofs: use meta buffers for xattr operations")
Signed-off-by: Jia Zhu <zhujia.zj@bytedance.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Fixes: bb88e8d ("erofs: use meta buffers for xattr operations")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Author: Jia Zhu

fs/erofs/xattr.c

@@ -89,13 +89,11 @@ static int erofs_init_inode_xattrs(struct inode *inode)
 	    vi->xattr_isize - sizeof(struct erofs_xattr_ibody_header)) {
 		erofs_err(sb, "invalid h_shared_count %u @ nid %llu",
 			  vi->xattr_shared_count, vi->nid);
-		erofs_put_metabuf(&buf);
 		ret = -EFSCORRUPTED;
 		goto out_unlock;
 	}
 	vi->xattr_shared_xattrs = kmalloc_objs(uint, vi->xattr_shared_count);
 	if (!vi->xattr_shared_xattrs) {
-		erofs_put_metabuf(&buf);
 		ret = -ENOMEM;
 		goto out_unlock;
 	}
@@ -112,12 +110,12 @@ static int erofs_init_inode_xattrs(struct inode *inode)
 		}
 		vi->xattr_shared_xattrs[i] = le32_to_cpu(*xattr_id);
 	}
-	erofs_put_metabuf(&buf);
 
 	/* paired with smp_mb() at the beginning of the function. */
 	smp_mb();
 	set_bit(EROFS_I_EA_INITED_BIT, &vi->flags);
 out_unlock:
+	erofs_put_metabuf(&buf);
 	clear_and_wake_up_bit(EROFS_I_BL_XATTR_BIT, &vi->flags);
 	return ret;
 }