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CIFS: Mask off signals when sending SMB packets

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We don't want to break SMB sessions if we receive signals when
sending packets through the network. Fix it by masking off signals
inside __smb_send_rqst() to avoid partial packet sends due to
interrupts.

Return -EINTR if a signal is pending and only a part of the packet
was sent. Return a success status code if the whole packet was sent
regardless of signal being pending or not. This keeps a mid entry
for the request in the pending queue and allows the demultiplex
thread to handle a response from the server properly.

Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Pavel Shilovsky 2019-03-05 15:51:57 -08:00 committed by Steve French
parent afc18a6f7b
commit b30c74c73c
1 changed files with 38 additions and 3 deletions
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41
fs/cifs/transport.c
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@ -33,6 +33,7 @@
#include <linux/uaccess.h>
#include <asm/processor.h>
#include <linux/mempool.h>
#include <linux/signal.h>
#include "cifspdu.h"
#include "cifsglob.h"
#include "cifsproto.h"
@ -291,6 +292,7 @@ __smb_send_rqst(struct TCP_Server_Info *server, int num_rqst,
int n_vec;
unsigned int send_length = 0;
unsigned int i, j;
sigset_t mask, oldmask;
size_t total_len = 0, sent, size;
struct socket *ssocket = server->ssocket;
struct msghdr smb_msg;
@ -305,6 +307,11 @@ __smb_send_rqst(struct TCP_Server_Info *server, int num_rqst,
if (ssocket == NULL)
return -EAGAIN;
if (signal_pending(current)) {
cifs_dbg(FYI, "signal is pending before sending any data\n");
return -EINTR;
}
/* cork the socket */
kernel_setsockopt(ssocket, SOL_TCP, TCP_CORK,
(char *)&val, sizeof(val));
@ -313,6 +320,16 @@ __smb_send_rqst(struct TCP_Server_Info *server, int num_rqst,
send_length += smb_rqst_len(server, &rqst[j]);
rfc1002_marker = cpu_to_be32(send_length);
/*
* We should not allow signals to interrupt the network send because
* any partial send will cause session reconnects thus increasing
* latency of system calls and overload a server with unnecessary
* requests.
*/
sigfillset(&mask);
sigprocmask(SIG_BLOCK, &mask, &oldmask);
/* Generate a rfc1002 marker for SMB2+ */
if (server->vals->header_preamble_size == 0) {
struct kvec hiov = {
@ -322,7 +339,7 @@ __smb_send_rqst(struct TCP_Server_Info *server, int num_rqst,
iov_iter_kvec(&smb_msg.msg_iter, WRITE, &hiov, 1, 4);
rc = smb_send_kvec(server, &smb_msg, &sent);
if (rc < 0)
goto uncork;
goto unmask;
total_len += sent;
send_length += 4;
@ -344,7 +361,7 @@ __smb_send_rqst(struct TCP_Server_Info *server, int num_rqst,
rc = smb_send_kvec(server, &smb_msg, &sent);
if (rc < 0)
goto uncork;
goto unmask;
total_len += sent;
@ -366,7 +383,25 @@ __smb_send_rqst(struct TCP_Server_Info *server, int num_rqst,
}
}
uncork:
unmask:
sigprocmask(SIG_SETMASK, &oldmask, NULL);
/*
* If signal is pending but we have already sent the whole packet to
* the server we need to return success status to allow a corresponding
* mid entry to be kept in the pending requests queue thus allowing
* to handle responses from the server by the client.
*
* If only part of the packet has been sent there is no need to hide
* interrupt because the session will be reconnected anyway, so there
* won't be any response from the server to handle.
*/
if (signal_pending(current) && (total_len != send_length)) {
cifs_dbg(FYI, "signal is pending after attempt to send\n");
rc = -EINTR;
}
/* uncork it */
val = 0;
kernel_setsockopt(ssocket, SOL_TCP, TCP_CORK,