diff options
| author | Pavel Shilovsky <pshilov@microsoft.com> | 2019-11-21 11:35:13 -0800 |
|---|---|---|
| committer | Steve French <stfrench@microsoft.com> | 2019-11-25 01:14:53 -0600 |
| commit | 86a7964be7afaf3df6b64faaa10a7032d2444e51 (patch) | |
| tree | 5fcf70bf32a87191bd6c4f31a59544b6b7741d22 /fs/cifs/connect.c | |
| parent | 9150c3adbf24d77cfba37f03639d4a908ca4ac25 (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 'fs/cifs/connect.c')
| -rw-r--r-- | fs/cifs/connect.c | 15 |
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) spin_unlock(&GlobalMid_Lock); } +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)) return; + 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? */ |