cifs: protect all accesses to chan_* with chan_lock

A spin lock called chan_lock was introduced recently.
But not all accesses were protected. Doing that with
this change.

To make sure that a channel is not freed when in use,
we need to introduce a ref count. But today, we don't
ever free channels.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: sprasad-microsoft

fs/cifs/connect.c

@@ -1831,7 +1831,6 @@ void cifs_put_smb_ses(struct cifs_ses *ses)
 
 	spin_lock(&ses->chan_lock);
 	chan_count = ses->chan_count;
-	spin_unlock(&ses->chan_lock);
 
 	/* close any extra channels */
 	if (chan_count > 1) {
@@ -1848,6 +1847,7 @@ void cifs_put_smb_ses(struct cifs_ses *ses)
 			ses->chans[i].server = NULL;
 		}
 	}
+	spin_unlock(&ses->chan_lock);
 
 	sesInfoFree(ses);
 	cifs_put_tcp_session(server, 0);
@@ -2123,8 +2123,10 @@ cifs_get_smb_ses(struct TCP_Server_Info *server, struct smb3_fs_context *ctx)
 	mutex_unlock(&ses->session_mutex);
 
 	/* each channel uses a different signing key */
+	spin_lock(&ses->chan_lock);
 	memcpy(ses->chans[0].signkey, ses->smb3signingkey,
 	       sizeof(ses->smb3signingkey));
+	spin_unlock(&ses->chan_lock);
 
 	if (rc)
 		goto get_ses_fail;

fs/cifs/sess.c

@@ -65,6 +65,8 @@ bool is_ses_using_iface(struct cifs_ses *ses, struct cifs_server_iface *iface)
 	return false;
 }
 
+/* channel helper functions. assumed that chan_lock is held by caller. */
+
 unsigned int
 cifs_ses_get_chan_index(struct cifs_ses *ses,
 			struct TCP_Server_Info *server)
@@ -134,10 +136,10 @@ int cifs_try_adding_channels(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses)
 	left = ses->chan_max - ses->chan_count;
 
 	if (left <= 0) {
+		spin_unlock(&ses->chan_lock);
 		cifs_dbg(FYI,
 			 "ses already at max_channels (%zu), nothing to open\n",
 			 ses->chan_max);
-		spin_unlock(&ses->chan_lock);
 		return 0;
 	}
 
@@ -369,12 +371,14 @@ void cifs_ses_mark_for_reconnect(struct cifs_ses *ses)
 {
 	int i;
 
+	spin_lock(&cifs_tcp_ses_lock);
+	spin_lock(&ses->chan_lock);
 	for (i = 0; i < ses->chan_count; i++) {
-		spin_lock(&cifs_tcp_ses_lock);
 		if (ses->chans[i].server->tcpStatus != CifsExiting)
 			ses->chans[i].server->tcpStatus = CifsNeedReconnect;
-		spin_unlock(&cifs_tcp_ses_lock);
 	}
+	spin_unlock(&ses->chan_lock);
+	spin_unlock(&cifs_tcp_ses_lock);
 }
 
 static __u32 cifs_ssetup_hdr(struct cifs_ses *ses,

fs/cifs/smb2pdu.c

@@ -244,10 +244,10 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon,
 		spin_unlock(&ses->chan_lock);
 		return 0;
 	}
+	spin_unlock(&ses->chan_lock);
 	cifs_dbg(FYI, "sess reconnect mask: 0x%lx, tcon reconnect: %d",
 		 tcon->ses->chans_need_reconnect,
 		 tcon->need_reconnect);
-	spin_unlock(&ses->chan_lock);
 
 	nls_codepage = load_nls_default();
 
@@ -3835,11 +3835,13 @@ void smb2_reconnect_server(struct work_struct *work)
 		 * binding session, but tcon is healthy (some other channel
 		 * is active)
 		 */
+		spin_lock(&ses->chan_lock);
 		if (!tcon_selected && cifs_chan_needs_reconnect(ses, server)) {
 			list_add_tail(&ses->rlist, &tmp_ses_list);
 			ses_selected = ses_exist = true;
 			ses->ses_count++;
 		}
+		spin_unlock(&ses->chan_lock);
 	}
 	/*
 	 * Get the reference to server struct to be sure that the last call of

fs/cifs/smb2transport.c

@@ -100,6 +100,7 @@ int smb2_get_sign_key(__u64 ses_id, struct TCP_Server_Info *server, u8 *key)
 	goto out;
 
 found:
+	spin_lock(&ses->chan_lock);
 	if (cifs_chan_needs_reconnect(ses, server) &&
 	    !CIFS_ALL_CHANS_NEED_RECONNECT(ses)) {
 		/*
@@ -108,6 +109,7 @@ int smb2_get_sign_key(__u64 ses_id, struct TCP_Server_Info *server, u8 *key)
 		 * session key
 		 */
 		memcpy(key, ses->smb3signingkey, SMB3_SIGN_KEY_SIZE);
+		spin_unlock(&ses->chan_lock);
 		goto out;
 	}
 
@@ -119,9 +121,11 @@ int smb2_get_sign_key(__u64 ses_id, struct TCP_Server_Info *server, u8 *key)
 		chan = ses->chans + i;
 		if (chan->server == server) {
 			memcpy(key, chan->signkey, SMB3_SIGN_KEY_SIZE);
+			spin_unlock(&ses->chan_lock);
 			goto out;
 		}
 	}
+	spin_unlock(&ses->chan_lock);
 
 	cifs_dbg(VFS,
 		 "%s: Could not find channel signing key for session 0x%llx\n",
@@ -430,8 +434,10 @@ generate_smb3signingkey(struct cifs_ses *ses,
 			return rc;
 
 		/* safe to access primary channel, since it will never go away */
+		spin_lock(&ses->chan_lock);
 		memcpy(ses->chans[0].signkey, ses->smb3signingkey,
 		       SMB3_SIGN_KEY_SIZE);
+		spin_unlock(&ses->chan_lock);
 
 		rc = generate_key(ses, ptriplet->encryption.label,
 				  ptriplet->encryption.context,

fs/cifs/transport.c

@@ -1049,7 +1049,10 @@ struct TCP_Server_Info *cifs_pick_channel(struct cifs_ses *ses)
 
 	/* round robin */
 	index = (uint)atomic_inc_return(&ses->chan_seq);
+
+	spin_lock(&ses->chan_lock);
 	index %= ses->chan_count;
+	spin_unlock(&ses->chan_lock);
 
 	return ses->chans[index].server;
 }