cifs: fix potential double put of TCP session reference

commit 460cf3411b858ad509d5255e0dfaf862a83c0299 upstream.

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.

Reviewed-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 2208f06e4c45ec17d1908b5435ee556be54d6dbe..fa1039a7ac4099bc5ce59bfa289ef8bc2526861e 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -1647,9 +1647,6 @@ 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) {
@@ -1672,6 +1669,9 @@ 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;
        }