CIFS: Do not reconnect TCP session in add_credits()
When executing add_credits() we currently call cifs_reconnect()
if the number of credits is zero and there are no requests in
flight. In this case we may call cifs_reconnect() recursively
twice and cause memory corruption given the following sequence
of functions:
mid1.callback() -> add_credits() -> cifs_reconnect() ->
-> mid2.callback() -> add_credits() -> cifs_reconnect().
Fix this by avoiding to call cifs_reconnect() in add_credits()
and checking for zero credits in the demultiplex thread.
Cc: <stable@vger.kernel.org>
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 1d3ce12..fa8d2e10 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -34,6 +34,7 @@
#include "cifs_ioctl.h"
#include "smbdirect.h"
+/* Change credits for different ops and return the total number of credits */
static int
change_conf(struct TCP_Server_Info *server)
{
@@ -41,17 +42,15 @@ change_conf(struct TCP_Server_Info *server)
server->oplock_credits = server->echo_credits = 0;
switch (server->credits) {
case 0:
- return -1;
+ return 0;
case 1:
server->echoes = false;
server->oplocks = false;
- cifs_dbg(VFS, "disabling echoes and oplocks\n");
break;
case 2:
server->echoes = true;
server->oplocks = false;
server->echo_credits = 1;
- cifs_dbg(FYI, "disabling oplocks\n");
break;
default:
server->echoes = true;
@@ -64,14 +63,15 @@ change_conf(struct TCP_Server_Info *server)
server->echo_credits = 1;
}
server->credits -= server->echo_credits + server->oplock_credits;
- return 0;
+ return server->credits + server->echo_credits + server->oplock_credits;
}
static void
smb2_add_credits(struct TCP_Server_Info *server, const unsigned int add,
const int optype)
{
- int *val, rc = 0;
+ int *val, rc = -1;
+
spin_lock(&server->req_lock);
val = server->ops->get_credits_field(server, optype);
@@ -101,8 +101,26 @@ smb2_add_credits(struct TCP_Server_Info *server, const unsigned int add,
}
spin_unlock(&server->req_lock);
wake_up(&server->request_q);
- if (rc)
- cifs_reconnect(server);
+
+ if (server->tcpStatus == CifsNeedReconnect)
+ return;
+
+ switch (rc) {
+ case -1:
+ /* change_conf hasn't been executed */
+ break;
+ case 0:
+ cifs_dbg(VFS, "Possible client or server bug - zero credits\n");
+ break;
+ case 1:
+ cifs_dbg(VFS, "disabling echoes and oplocks\n");
+ break;
+ case 2:
+ cifs_dbg(FYI, "disabling oplocks\n");
+ break;
+ default:
+ cifs_dbg(FYI, "add %u credits total=%d\n", add, rc);
+ }
}
static void