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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>
This commit is contained in:
Pavel Shilovsky 2019-01-18 17:25:36 -08:00 committed by Steve French
parent b0b2cac7e2
commit ef68e83184
2 changed files with 46 additions and 7 deletions
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21
fs/cifs/connect.c
View File

@ -720,6 +720,21 @@ server_unresponsive(struct TCP_Server_Info *server)
return false;
}
static inline bool
zero_credits(struct TCP_Server_Info *server)
{
int val;
spin_lock(&server->req_lock);
val = server->credits + server->echo_credits + server->oplock_credits;
if (server->in_flight == 0 && val == 0) {
spin_unlock(&server->req_lock);
return true;
}
spin_unlock(&server->req_lock);
return false;
}
static int
cifs_readv_from_socket(struct TCP_Server_Info *server, struct msghdr *smb_msg)
{
@ -732,6 +747,12 @@ cifs_readv_from_socket(struct TCP_Server_Info *server, struct msghdr *smb_msg)
for (total_read = 0; msg_data_left(smb_msg); total_read += length) {
try_to_freeze();
/* reconnect if no credits and no requests in flight */
if (zero_credits(server)) {
cifs_reconnect(server);
return -ECONNABORTED;
}
if (server_unresponsive(server))
return -ECONNABORTED;
if (cifs_rdma_enabled(server) && server->smbd_conn)

32
fs/cifs/smb2ops.c
View File

@ -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