cifs: avoid races in parallel reconnects in smb1

Prevent multiple threads of doing negotiate, session setup and tree
connect by holding @ses->session_mutex in cifs_reconnect_tcon() while
reconnecting session and tcon.

Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 38a697eca3050d5a862a7ef917f84edec9d4ba3e..c9d57ba84be414f2a82fdd8c8830da3baef475b1 100644 (file)
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -71,7 +71,7 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command)
        int rc;
        struct cifs_ses *ses;
        struct TCP_Server_Info *server;
-       struct nls_table *nls_codepage;
+       struct nls_table *nls_codepage = NULL;
 
        /*
         * SMBs NegProt, SessSetup, uLogoff do not have tcon yet so check for
@@ -99,6 +99,7 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command)
        }
        spin_unlock(&tcon->tc_lock);
 
+again:
        rc = cifs_wait_for_server_reconnect(server, tcon->retry);
        if (rc)
                return rc;
@@ -110,8 +111,7 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command)
        }
        spin_unlock(&ses->chan_lock);
 
-       nls_codepage = load_nls_default();
-
+       mutex_lock(&ses->session_mutex);
        /*
         * Recheck after acquire mutex. If another thread is negotiating
         * and the server never sends an answer the socket will be closed
@@ -120,29 +120,38 @@ cifs_reconnect_tcon(struct cifs_tcon *tcon, int smb_command)
        spin_lock(&server->srv_lock);
        if (server->tcpStatus == CifsNeedReconnect) {
                spin_unlock(&server->srv_lock);
+               mutex_lock(&ses->session_mutex);
+
+               if (tcon->retry)
+                       goto again;
                rc = -EHOSTDOWN;
                goto out;
        }
        spin_unlock(&server->srv_lock);
 
+       nls_codepage = load_nls_default();
+
        /*
         * need to prevent multiple threads trying to simultaneously
         * reconnect the same SMB session
         */
+       spin_lock(&ses->ses_lock);
        spin_lock(&ses->chan_lock);
-       if (!cifs_chan_needs_reconnect(ses, server)) {
+       if (!cifs_chan_needs_reconnect(ses, server) &&
+           ses->ses_status == SES_GOOD) {
                spin_unlock(&ses->chan_lock);
+               spin_unlock(&ses->ses_lock);
 
                /* this means that we only need to tree connect */
                if (tcon->need_reconnect)
                        goto skip_sess_setup;
 
-               rc = -EHOSTDOWN;
+               mutex_unlock(&ses->session_mutex);
                goto out;
        }
        spin_unlock(&ses->chan_lock);
+       spin_unlock(&ses->ses_lock);
 
-       mutex_lock(&ses->session_mutex);
        rc = cifs_negotiate_protocol(0, ses, server);
        if (!rc)
                rc = cifs_setup_session(0, ses, server, nls_codepage);