On Mon, 2020-04-27 at 23:46 +0200, edward6@xxxxxxxxxxxxx wrote:
> From: Eduard Shishkin <edward6@xxxxxxxxxxxxx>
>
> In the function handle_session() variable @features always
> contains little endian order of bytes. Just because the feature
> bits are packed bytewise from left to right in
> encode_supported_features().
>
> However, test_bit(), called to check features availability, assumes
> the host order of bytes in that variable. This leads to problems on
> big endian architectures. Specifically it is impossible to mount
> ceph volume on s390.
>
> This patch adds conversion from little endian to the host order
> of bytes, thus fixing the problem.
>
> Signed-off-by: Eduard Shishkin <edward6@xxxxxxxxxxxxx>
> ---
> fs/ceph/mds_client.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
> index 486f91f..190598d 100644
> --- a/fs/ceph/mds_client.c
> +++ b/fs/ceph/mds_client.c
> @@ -3252,7 +3252,7 @@ static void handle_session(struct ceph_mds_session *session,
> struct ceph_mds_session_head *h;
> u32 op;
> u64 seq;
> - unsigned long features = 0;
> + __le64 features = 0;
> int wake = 0;
> bool blacklisted = false;
>
> @@ -3301,7 +3301,7 @@ static void handle_session(struct ceph_mds_session *session,
> if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
> pr_info("mds%d reconnect success\n", session->s_mds);
> session->s_state = CEPH_MDS_SESSION_OPEN;
> - session->s_features = features;
> + session->s_features = le64_to_cpu(features);
> renewed_caps(mdsc, session, 0);
> wake = 1;
> if (mdsc->stopping)
(cc'ing Zheng since he did the original patches here)
Thanks Eduard. The problem is real, but I think we can just do the
conversion during the decode.
The feature mask words sent by the MDS are 64 bits, so if it's smaller
we can assume that it's malformed. So, I don't think we need to handle
the case where it's smaller than 8 bytes.
How about this patch instead?
--------------------------8<-----------------------------
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.
Reported-by: Eduard Shishkin <edward6@xxxxxxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/ceph/mds_client.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index a8a5b98148ec..6c283c52d401 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -3260,8 +3260,7 @@ 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;
@@ -3280,9 +3279,8 @@ 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);
--
2.26.1
