linux-kernel - [PATCH 5.6 086/118] ceph: fix endianness bug when handling MDS session feature bits

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Date:   Wed, 13 May 2020 11:45:05 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jeff Layton <jlayton@...nel.org>,
        "Yan, Zheng" <zyan@...hat.com>, Ilya Dryomov <idryomov@...il.com>,
        Eduard Shishkin <edward6@...ux.ibm.com>
Subject: [PATCH 5.6 086/118] ceph: fix endianness bug when handling MDS session feature bits

From: Jeff Layton <jlayton@...nel.org>

commit 0fa8263367db9287aa0632f96c1a5f93cc478150 upstream.

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@...r.kernel.org
Reported-and-Tested-by: Eduard Shishkin <edward6@...ux.ibm.com>
Signed-off-by: Jeff Layton <jlayton@...nel.org>
Reviewed-by: "Yan, Zheng" <zyan@...hat.com>
Signed-off-by: Ilya Dryomov <idryomov@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/ceph/mds_client.c |    8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -3116,8 +3116,7 @@ static void handle_session(struct ceph_m
 	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;
 
@@ -3136,9 +3135,8 @@ static void handle_session(struct ceph_m
 			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);