ceph: fix use-after-free on symlink traversal

[ Upstream commit daf5cc27eed99afdea8d96e71b89ba41f5406ef6 ]

free the symlink body after the same RCU delay we have for freeing the
struct inode itself, so that traversal during RCU pathwalk wouldn't step
into freed memory.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 4055ab4..3e518c2 100644 (file)
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -524,6 +524,7 @@ static void ceph_i_callback(struct rcu_head *head)
        struct inode *inode = container_of(head, struct inode, i_rcu);
        struct ceph_inode_info *ci = ceph_inode(inode);
 
+       kfree(ci->i_symlink);
        kmem_cache_free(ceph_inode_cachep, ci);
 }
 
@@ -561,7 +562,6 @@ void ceph_destroy_inode(struct inode *inode)
                ceph_put_snap_realm(mdsc, realm);
        }
 
-       kfree(ci->i_symlink);
        while ((n = rb_first(&ci->i_fragtree)) != NULL) {
                frag = rb_entry(n, struct ceph_inode_frag, node);
                rb_erase(n, &ci->i_fragtree);