[PATCH AUTOSEL 6.2 60/60] cifs: prevent data race in smb2_reconnect()

Sasha Levin
2023-02-27T02:06:04Z

From: Paulo Alcantara <pc@cjr.nz>

[ Upstream commit 3c0070f54b3128de498c2dd9934a21f0dd867111 ]

Make sure to get an up-to-date TCP_Server_Info::nr_targets value prior
to waiting the server to be reconnected in smb2_reconnect(). It is
set in cifs_tcp_ses_needs_reconnect() and protected by
TCP_Server_Info::srv_lock.

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/cifs/smb2pdu.c | 119 +++++++++++++++++++++++++---------------------
1 file changed, 64 insertions(+), 55 deletions(-)

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 2c9ffa921e6f6..2d5c3df2277d4 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -139,6 +139,66 @@ smb2_hdr_assemble(struct smb2_hdr *shdr, __le16 smb2_cmd,
return;
}

+static int wait_for_server_reconnect(struct TCP_Server_Info *server,
+ __le16 smb2_command, bool retry)
+{
+ int timeout = 10;
+ int rc;
+
+ spin_lock(&server->srv_lock);
+ if (server->tcpStatus != CifsNeedReconnect) {
+ spin_unlock(&server->srv_lock);
+ return 0;
+ }
+ timeout *= server->nr_targets;
+ spin_unlock(&server->srv_lock);
+
+ /*
+ * Return to caller for TREE_DISCONNECT and LOGOFF and CLOSE
+ * here since they are implicitly done when session drops.
+ */
+ switch (smb2_command) {
+ /*
+ * BB Should we keep oplock break and add flush to exceptions?
+ */
+ case SMB2_TREE_DISCONNECT:
+ case SMB2_CANCEL:
+ case SMB2_CLOSE:
+ case SMB2_OPLOCK_BREAK:
+ return -EAGAIN;
+ }
+
+ /*
+ * Give demultiplex thread up to 10 seconds to each target available for
+ * reconnect -- should be greater than cifs socket timeout which is 7
+ * seconds.
+ *
+ * On "soft" mounts we wait once. Hard mounts keep retrying until
+ * process is killed or server comes back on-line.
+ */
+ do {
+ rc = wait_event_interruptible_timeout(server->response_q,
+ (server->tcpStatus != CifsNeedReconnect),
+ timeout * HZ);
+ if (rc < 0) {
+ cifs_dbg(FYI, "%s: aborting reconnect due to received signal\n",
+ __func__);
+ return -ERESTARTSYS;
+ }
+
+ /* are we still trying to reconnect? */
+ spin_lock(&server->srv_lock);
+ if (server->tcpStatus != CifsNeedReconnect) {
+ spin_unlock(&server->srv_lock);
+ return 0;
+ }
+ spin_unlock(&server->srv_lock);
+ } while (retry);
+
+ cifs_dbg(FYI, "%s: gave up waiting on reconnect\n", __func__);
+ return -EHOSTDOWN;
+}
+
static int
smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon,
struct TCP_Server_Info *server)
@@ -146,7 +206,6 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon,
int rc = 0;
struct nls_table *nls_codepage;
struct cifs_ses *ses;
- int retries;

/*
* SMB2s NegProt, SessSetup, Logoff do not have tcon yet so
@@ -184,61 +243,11 @@ smb2_reconnect(__le16 smb2_command, struct cifs_tcon *tcon,
(!tcon->ses->server) || !server)
return -EIO;

- ses = tcon->ses;
- retries = server->nr_targets;
-
- /*
- * Give demultiplex thread up to 10 seconds to each target available for
- * reconnect -- should be greater than cifs socket timeout which is 7
- * seconds.
- */
- while (server->tcpStatus == CifsNeedReconnect) {
- /*
- * Return to caller for TREE_DISCONNECT and LOGOFF and CLOSE
- * here since they are implicitly done when session drops.
- */
- switch (smb2_command) {
- /*
- * BB Should we keep oplock break and add flush to exceptions?
- */
- case SMB2_TREE_DISCONNECT:
- case SMB2_CANCEL:
- case SMB2_CLOSE:
- case SMB2_OPLOCK_BREAK:
- return -EAGAIN;
- }
-
- rc = wait_event_interruptible_timeout(server->response_q,
- (server->tcpStatus != CifsNeedReconnect),
- 10 * HZ);
- if (rc < 0) {
- cifs_dbg(FYI, "%s: aborting reconnect due to a received signal by the process\n",
- __func__);
- return -ERESTARTSYS;
- }
-
- /* are we still trying to reconnect? */
- spin_lock(&server->srv_lock);
- if (server->tcpStatus != CifsNeedReconnect) {
- spin_unlock(&server->srv_lock);
- break;
- }
- spin_unlock(&server->srv_lock);
-
- if (retries && --retries)
- continue;
+ rc = wait_for_server_reconnect(server, smb2_command, tcon->retry);
+ if (rc)
+ return rc;

- /*
- * on "soft" mounts we wait once. Hard mounts keep
- * retrying until process is killed or server comes
- * back on-line
- */
- if (!tcon->retry) {
- cifs_dbg(FYI, "gave up waiting on reconnect in smb_init\n");
- return -EHOSTDOWN;
- }
- retries = server->nr_targets;
- }
+ ses = tcon->ses;

spin_lock(&ses->chan_lock);
if (!cifs_chan_needs_reconnect(ses, server) && !tcon->need_reconnect) {
--
2.39.0