Commit 53a27c6f authored Nov 12, 2020 by Luis Henriques Committed by Greg Kroah-Hartman Dec 30, 2020

ceph: fix race in concurrent __ceph_remove_cap invocations

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>

parent 709ed96f

fs/ceph/caps.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -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)