From: Luis Henriques lhenriques@suse.de
commit e5cafce3ad0f8652d6849314d951459c2bff7233 upstream.
A NULL pointer dereference may occur in __ceph_remove_cap with some of the callbacks used in ceph_iterate_session_caps, namely trim_caps_cb and remove_session_caps_cb. Those callers hold the session->s_mutex, so they are prevented from concurrent execution, but ceph_evict_inode does not.
Since the callers of this function hold the i_ceph_lock, the fix is simply a matter of returning immediately if caps->ci is NULL.
Cc: stable@vger.kernel.org URL: https://tracker.ceph.com/issues/43272 Suggested-by: Jeff Layton jlayton@kernel.org Signed-off-by: Luis Henriques lhenriques@suse.de Reviewed-by: Jeff Layton jlayton@kernel.org Signed-off-by: Ilya Dryomov idryomov@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/ceph/caps.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c index c0dbf8b7762b..6e871a382209 100644 --- a/fs/ceph/caps.c +++ b/fs/ceph/caps.c @@ -1047,12 +1047,19 @@ void __ceph_remove_cap(struct ceph_cap *cap, bool queue_release) { struct ceph_mds_session *session = cap->session; struct ceph_inode_info *ci = cap->ci; - struct ceph_mds_client *mdsc = - ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc; + struct ceph_mds_client *mdsc; int removed = 0;
+ /* 'ci' being NULL means the remove have already occurred */ + if (!ci) { + dout("%s: cap inode is NULL\n", __func__); + return; + } + dout("__ceph_remove_cap %p from %p\n", cap, &ci->vfs_inode);
+ mdsc = ceph_inode_to_client(&ci->vfs_inode)->mdsc; + /* remove from inode's cap rbtree, and clear auth cap */ rb_erase(&cap->ci_node, &ci->i_caps); if (ci->i_auth_cap == cap)