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CIFS: Do not miss cancelled OPEN responses

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When an OPEN command is cancelled we mark a mid as
cancelled and let the demultiplex thread process it
by closing an open handle. The problem is there is
a race between a system call thread and the demultiplex
thread and there may be a situation when the mid has
been already processed before it is set as cancelled.

Fix this by processing cancelled requests when mids
are being destroyed which means that there is only
one thread referencing a particular mid. Also set
mids as cancelled unconditionally on their state.

Cc: Stable <stable@vger.kernel.org>
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>
This commit is contained in:
Pavel Shilovsky 2019-11-21 11:35:14 -08:00 committed by Steve French
parent 86a7964be7
commit 7b71843fa7
2 changed files with 8 additions and 8 deletions
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6
fs/cifs/connect.c
View file

@ -1237,12 +1237,6 @@ cifs_demultiplex_thread(void *p)
for (i = 0; i < num_mids; i++) {
if (mids[i] != NULL) {
mids[i]->resp_buf_size = server->pdu_size;
if ((mids[i]->mid_flags & MID_WAIT_CANCELLED) &&
mids[i]->mid_state == MID_RESPONSE_RECEIVED &&
server->ops->handle_cancelled_mid)
server->ops->handle_cancelled_mid(
mids[i]->resp_buf,
server);
if (!mids[i]->multiRsp || mids[i]->multiEnd)
mids[i]->callback(mids[i]);

10
fs/cifs/transport.c
View file

@ -93,8 +93,14 @@ static void _cifs_mid_q_entry_release(struct kref *refcount)
__u16 smb_cmd = le16_to_cpu(midEntry->command);
unsigned long now;
unsigned long roundtrip_time;
struct TCP_Server_Info *server = midEntry->server;
#endif
struct TCP_Server_Info *server = midEntry->server;
if (midEntry->resp_buf && (midEntry->mid_flags & MID_WAIT_CANCELLED) &&
midEntry->mid_state == MID_RESPONSE_RECEIVED &&
server->ops->handle_cancelled_mid)
server->ops->handle_cancelled_mid(midEntry->resp_buf, server);
midEntry->mid_state = MID_FREE;
atomic_dec(&midCount);
if (midEntry->large_buf)
@ -1119,8 +1125,8 @@ compound_send_recv(const unsigned int xid, struct cifs_ses *ses,
midQ[i]->mid, le16_to_cpu(midQ[i]->command));
send_cancel(server, &rqst[i], midQ[i]);
spin_lock(&GlobalMid_Lock);
midQ[i]->mid_flags |= MID_WAIT_CANCELLED;
if (midQ[i]->mid_state == MID_REQUEST_SUBMITTED) {
midQ[i]->mid_flags |= MID_WAIT_CANCELLED;
midQ[i]->callback = cifs_cancelled_callback;
cancelled_mid[i] = true;
credits[i].value = 0;