[PATCH AUTOSEL 4.14 36/43] ceph: fix use-after-free on symlink traversal

Sasha Levin
2019-04-22T19:57:35Z

From: Al Viro <viro@zeniv.linux.org.uk>

[ 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>
---
fs/ceph/inode.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index a1492bdc6d03..f2b722f0df5d 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -520,6 +520,7 @@ 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);
}

@@ -551,7 +552,6 @@ 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);
--
2.19.1