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CIFS: Fix null pointer deref during read resp processing 

Currently during receiving a read response mid->resp_buf can be
NULL when it is being passed to cifs_discard_remaining_data() from
cifs_readv_discard(). Fix it by always passing server->smallbuf
instead and initializing mid->resp_buf at the end of read response
processing.

Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
CC: Stable <stable@vger.kernel.org>
Acked-by: Sachin Prabhu <sprabhu@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
This commit is contained in:
Pavel Shilovsky 2017-04-10 10:31:33 -07:00 committed by Steve French
parent c08e611b7d
commit 350be257ea
3 changed files with 11 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
fs/cifs/cifsproto.h
View File

@ -79,8 +79,7 @@ extern void cifs_delete_mid(struct mid_q_entry *mid);
extern void cifs_wake_up_task(struct mid_q_entry *mid);
extern int cifs_handle_standard(struct TCP_Server_Info *server,
struct mid_q_entry *mid);
extern int cifs_discard_remaining_data(struct TCP_Server_Info *server,
char *buf);
extern int cifs_discard_remaining_data(struct TCP_Server_Info *server);
extern int cifs_call_async(struct TCP_Server_Info *server,
struct smb_rqst *rqst,
mid_receive_t *receive, mid_callback_t *callback,

15
fs/cifs/cifssmb.c
View File

@ -1400,9 +1400,9 @@ openRetry:
* current bigbuf.
*/
int
cifs_discard_remaining_data(struct TCP_Server_Info *server, char *buf)
cifs_discard_remaining_data(struct TCP_Server_Info *server)
{
unsigned int rfclen = get_rfc1002_length(buf);
unsigned int rfclen = get_rfc1002_length(server->smallbuf);
int remaining = rfclen + 4 - server->total_read;
while (remaining > 0) {
@ -1426,8 +1426,10 @@ cifs_readv_discard(struct TCP_Server_Info *server, struct mid_q_entry *mid)
int length;
struct cifs_readdata *rdata = mid->callback_data;
length = cifs_discard_remaining_data(server, mid->resp_buf);
length = cifs_discard_remaining_data(server);
dequeue_mid(mid, rdata->result);
mid->resp_buf = server->smallbuf;
server->smallbuf = NULL;
return length;
}
@ -1459,7 +1461,7 @@ cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid)
if (server->ops->is_status_pending &&
server->ops->is_status_pending(buf, server, 0)) {
cifs_discard_remaining_data(server, buf);
cifs_discard_remaining_data(server);
return -1;
}
@ -1519,9 +1521,6 @@ cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid)
cifs_dbg(FYI, "0: iov_base=%p iov_len=%u\n",
rdata->iov[0].iov_base, server->total_read);
mid->resp_buf = server->smallbuf;
server->smallbuf = NULL;
/* how much data is in the response? */
data_len = server->ops->read_data_length(buf);
if (data_offset + data_len > buflen) {
@ -1544,6 +1543,8 @@ cifs_readv_receive(struct TCP_Server_Info *server, struct mid_q_entry *mid)
return cifs_readv_discard(server, mid);
dequeue_mid(mid, false);
mid->resp_buf = server->smallbuf;
server->smallbuf = NULL;
return length;
}

4
fs/cifs/smb2ops.c
View File

@ -2195,7 +2195,7 @@ receive_encrypted_read(struct TCP_Server_Info *server, struct mid_q_entry **mid)
if (rc)
goto free_pages;
rc = cifs_discard_remaining_data(server, buf);
rc = cifs_discard_remaining_data(server);
if (rc)
goto free_pages;
@ -2221,7 +2221,7 @@ free_pages:
kfree(pages);
return rc;
discard_data:
cifs_discard_remaining_data(server, buf);
cifs_discard_remaining_data(server);
goto free_pages;
}