cifs: fix potential double put of TCP session reference

cifs_get_smb_ses must be called on a server pointer on which it holds an
active reference. It first does a search for an existing SMB session. If
it finds one, it'll put the server reference and then try to ensure that
the negprot is done, etc.

If it encounters an error at that point then it'll return an error.
There's a potential problem here though. When cifs_get_smb_ses returns
an error, the caller will also put the TCP server reference leading to a
double-put.

Fix this by having cifs_get_smb_ses only put the server reference if
it found an existing session that it could use and isn't returning an
error.

Cc: stable@kernel.org
Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 67dad54fbfa1ccb77f5414cd95e7f65e67cb7838..88c84a38bccb182c313316a172bbae39ba2ee38f 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1706,9 +1706,6 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info)
        if (ses) {
                cFYI(1, "Existing smb sess found (status=%d)", ses->status);
 
-               /* existing SMB ses has a server reference already */
-               cifs_put_tcp_session(server);
-
                mutex_lock(&ses->session_mutex);
                rc = cifs_negotiate_protocol(xid, ses);
                if (rc) {
@@ -1731,6 +1728,9 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb_vol *volume_info)
                        }
                }
                mutex_unlock(&ses->session_mutex);
+
+               /* existing SMB ses has a server reference already */
+               cifs_put_tcp_session(server);
                FreeXid(xid);
                return ses;
        }