ceph: fix endianness bug when handling MDS session feature bits

Eduard reported a problem mounting cephfs on s390 arch. The feature
mask sent by the MDS is little-endian, so we need to convert it
before storing and testing against it.

Cc: stable@vger.kernel.org
Reported-and-Tested-by: Eduard Shishkin <edward6@linux.ibm.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index 486f91f..7c63abf 100644 (file)
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -3251,8 +3251,7 @@ static void handle_session(struct ceph_mds_session *session,
        void *end = p + msg->front.iov_len;
        struct ceph_mds_session_head *h;
        u32 op;
-       u64 seq;
-       unsigned long features = 0;
+       u64 seq, features = 0;
        int wake = 0;
        bool blacklisted = false;
 
@@ -3271,9 +3270,8 @@ static void handle_session(struct ceph_mds_session *session,
                        goto bad;
                /* version >= 3, feature bits */
                ceph_decode_32_safe(&p, end, len, bad);
-               ceph_decode_need(&p, end, len, bad);
-               memcpy(&features, p, min_t(size_t, len, sizeof(features)));
-               p += len;
+               ceph_decode_64_safe(&p, end, features, bad);
+               p += len - sizeof(features);
        }
 
        mutex_lock(&mdsc->mutex);