ocfs2: check if cluster name exists before deref

Commit c74a3bdd9b52 ("ocfs2: add clustername to cluster connection") is
trying to strlcpy a string which was explicitly passed as NULL in the
very same patch, triggering a NULL ptr deref.

  BUG: unable to handle kernel NULL pointer dereference at           (null)
  IP: strlcpy (lib/string.c:388 lib/string.c:151)
  CPU: 19 PID: 19426 Comm: trinity-c19 Tainted: G        W     3.14.0-rc7-next-20140325-sasha-00014-g9476368-dirty #274
  RIP:  strlcpy (lib/string.c:388 lib/string.c:151)
  Call Trace:
   ocfs2_cluster_connect (fs/ocfs2/stackglue.c:350)
   ocfs2_cluster_connect_agnostic (fs/ocfs2/stackglue.c:396)
   user_dlm_register (fs/ocfs2/dlmfs/userdlm.c:679)
   dlmfs_mkdir (fs/ocfs2/dlmfs/dlmfs.c:503)
   vfs_mkdir (fs/namei.c:3467)
   SyS_mkdirat (fs/namei.c:3488 fs/namei.c:3472)
   tracesys (arch/x86/kernel/entry_64.S:749)

akpm: this patch probably disables the feature.  A temporary thing to
avoid triviel oopses.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/ocfs2/stackglue.c b/fs/ocfs2/stackglue.c
index 1324e6600e57378b8e4d1624dc1366af57fde7b2..ca5ce14cbddcef81498305f8ccbccc978750faed 100644 (file)
--- a/fs/ocfs2/stackglue.c
+++ b/fs/ocfs2/stackglue.c
@@ -346,7 +346,9 @@ int ocfs2_cluster_connect(const char *stack_name,
 
        strlcpy(new_conn->cc_name, group, GROUP_NAME_MAX + 1);
        new_conn->cc_namelen = grouplen;
-       strlcpy(new_conn->cc_cluster_name, cluster_name, CLUSTER_NAME_MAX + 1);
+       if (cluster_name_len)
+               strlcpy(new_conn->cc_cluster_name, cluster_name,
+                       CLUSTER_NAME_MAX + 1);
        new_conn->cc_cluster_name_len = cluster_name_len;
        new_conn->cc_recovery_handler = recovery_handler;
        new_conn->cc_recovery_data = recovery_data;