path: root/fs/cifs/connect.c
diff options
authorPavel Shilovsky <pshilov@microsoft.com>2019-11-21 11:35:13 -0800
committerSteve French <stfrench@microsoft.com>2019-11-25 01:14:53 -0600
commit86a7964be7afaf3df6b64faaa10a7032d2444e51 (patch)
tree5fcf70bf32a87191bd6c4f31a59544b6b7741d22 /fs/cifs/connect.c
parentCIFS: Close open handle after interrupted close (diff)
CIFS: Fix NULL pointer dereference in mid callback
There is a race between a system call processing thread and the demultiplex thread when mid->resp_buf becomes NULL and later is being accessed to get credits. It happens when the 1st thread wakes up before a mid callback is called in the 2nd one but the mid state has already been set to MID_RESPONSE_RECEIVED. This causes NULL pointer dereference in mid callback. Fix this by saving credits from the response before we update the mid state and then use this value in the mid callback rather then accessing a response buffer. Cc: Stable <stable@vger.kernel.org> Fixes: ee258d79159afed5 ("CIFS: Move credit processing to mid callbacks for SMB3") Tested-by: Frank Sorenson <sorenson@redhat.com> Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com> Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com> Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to '')
1 files changed, 15 insertions, 0 deletions
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index ccaa8bad336f..40b2a173ba0d 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -905,6 +905,20 @@ dequeue_mid(struct mid_q_entry *mid, bool malformed)
+static unsigned int
+smb2_get_credits_from_hdr(char *buffer, struct TCP_Server_Info *server)
+ struct smb2_sync_hdr *shdr = (struct smb2_sync_hdr *)buffer;
+ /*
+ * SMB1 does not use credits.
+ */
+ if (server->vals->header_preamble_size)
+ return 0;
+ return le16_to_cpu(shdr->CreditRequest);
static void
handle_mid(struct mid_q_entry *mid, struct TCP_Server_Info *server,
char *buf, int malformed)
@@ -912,6 +926,7 @@ handle_mid(struct mid_q_entry *mid, struct TCP_Server_Info *server,
if (server->ops->check_trans2 &&
server->ops->check_trans2(mid, server, buf, malformed))
+ mid->credits_received = smb2_get_credits_from_hdr(buf, server);
mid->resp_buf = buf;
mid->large_buf = server->large_buf;
/* Was previous buf put in mpx struct for multi-rsp? */