[PATCH] cifs: sanity check length of data to send before sending

[Jeff Layton]

We had a bug discovered recently where an upper layer function
(cifs_iovec_write) could pass down a smb_rqst with an invalid amount of
data in it. The length of the SMB frame would be correct, but the rqst
struct would cause smb_send_rqst to send nearly 4GB of data.

This should never be the case. Add some sanity checking to the beginning
of smb_send_rqst that ensures that the amount of data we're going to
send agrees with the length in the RFC1002 header. If it doesn't, WARN()
and return -EIO to the upper layers.

Signed-off-by: Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+***@public.gmane.org>
---
fs/cifs/transport.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)

diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index b37570952846..18cd5650a5fc 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -270,6 +270,26 @@ cifs_rqst_page_to_kvec(struct smb_rqst *rqst, unsigned int idx,
iov->iov_len = rqst->rq_pagesz;
}

+static unsigned long
+rqst_len(struct smb_rqst *rqst)
+{
+ unsigned int i;
+ struct kvec *iov = rqst->rq_iov;
+ unsigned long buflen = 0;
+
+ /* total up iov array first */
+ for (i = 0; i < rqst->rq_nvec; i++)
+ buflen += iov[i].iov_len;
+
+ /* add in the page array if there is one */
+ if (rqst->rq_npages) {
+ buflen += rqst->rq_pagesz * (rqst->rq_npages - 1);
+ buflen += rqst->rq_tailsz;
+ }
+
+ return buflen;
+}
+
static int
smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
{
@@ -277,6 +297,7 @@ smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
struct kvec *iov = rqst->rq_iov;
int n_vec = rqst->rq_nvec;
unsigned int smb_buf_length = get_rfc1002_length(iov[0].iov_base);
+ unsigned long send_length;
unsigned int i;
size_t total_len = 0, sent;
struct socket *ssocket = server->ssocket;
@@ -285,6 +306,14 @@ smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
if (ssocket == NULL)
return -ENOTSOCK;

+ /* sanity check send length */
+ send_length = rqst_len(rqst);
+ if (send_length != smb_buf_length + 4) {
+ WARN(1, "Send length mismatch(send_length=%lu smb_buf_length=%u)\n",
+ send_length, smb_buf_length);
+ return -EIO;
+ }
+
cifs_dbg(FYI, "Sending smb: smb_len=%u\n", smb_buf_length);
dump_smb(iov[0].iov_base, iov[0].iov_len);

[Sachin Prabhu]

Post by Jeff Layton
We had a bug discovered recently where an upper layer function
(cifs_iovec_write) could pass down a smb_rqst with an invalid amount of
data in it. The length of the SMB frame would be correct, but the rqst
struct would cause smb_send_rqst to send nearly 4GB of data.
This should never be the case. Add some sanity checking to the beginning
of smb_send_rqst that ensures that the amount of data we're going to
send agrees with the length in the RFC1002 header. If it doesn't, WARN()
and return -EIO to the upper layers.
---
fs/cifs/transport.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index b37570952846..18cd5650a5fc 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -270,6 +270,26 @@ cifs_rqst_page_to_kvec(struct smb_rqst *rqst, unsigned int idx,
iov->iov_len = rqst->rq_pagesz;
}
+static unsigned long
+rqst_len(struct smb_rqst *rqst)
+{
+ unsigned int i;
+ struct kvec *iov = rqst->rq_iov;
+ unsigned long buflen = 0;
+
+ /* total up iov array first */
+ for (i = 0; i < rqst->rq_nvec; i++)
+ buflen += iov[i].iov_len;
+
+ /* add in the page array if there is one */
+ if (rqst->rq_npages) {
+ buflen += rqst->rq_pagesz * (rqst->rq_npages - 1);
+ buflen += rqst->rq_tailsz;
+ }
+
+ return buflen;
+}
+
static int
smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
{
@@ -277,6 +297,7 @@ smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
struct kvec *iov = rqst->rq_iov;
int n_vec = rqst->rq_nvec;
unsigned int smb_buf_length = get_rfc1002_length(iov[0].iov_base);
+ unsigned long send_length;
unsigned int i;
size_t total_len = 0, sent;
struct socket *ssocket = server->ssocket;
@@ -285,6 +306,14 @@ smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
if (ssocket == NULL)
return -ENOTSOCK;
+ /* sanity check send length */
+ send_length = rqst_len(rqst);
+ if (send_length != smb_buf_length + 4) {
+ WARN(1, "Send length mismatch(send_length=%lu smb_buf_length=%u)\n",
+ send_length, smb_buf_length);
+ return -EIO;
+ }
+
cifs_dbg(FYI, "Sending smb: smb_len=%u\n", smb_buf_length);
dump_smb(iov[0].iov_base, iov[0].iov_len);

[Pavel Shilovsky]

Post by Jeff Layton
We had a bug discovered recently where an upper layer function
(cifs_iovec_write) could pass down a smb_rqst with an invalid amount of
data in it. The length of the SMB frame would be correct, but the rqst
struct would cause smb_send_rqst to send nearly 4GB of data.
This should never be the case. Add some sanity checking to the beginning
of smb_send_rqst that ensures that the amount of data we're going to
send agrees with the length in the RFC1002 header. If it doesn't, WARN()
and return -EIO to the upper layers.
---
fs/cifs/transport.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index b37570952846..18cd5650a5fc 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -270,6 +270,26 @@ cifs_rqst_page_to_kvec(struct smb_rqst *rqst, unsigned int idx,
iov->iov_len = rqst->rq_pagesz;
}
+static unsigned long
+rqst_len(struct smb_rqst *rqst)
+{
+ unsigned int i;
+ struct kvec *iov = rqst->rq_iov;
+ unsigned long buflen = 0;
+
+ /* total up iov array first */
+ for (i = 0; i < rqst->rq_nvec; i++)
+ buflen += iov[i].iov_len;
+
+ /* add in the page array if there is one */
+ if (rqst->rq_npages) {
+ buflen += rqst->rq_pagesz * (rqst->rq_npages - 1);
+ buflen += rqst->rq_tailsz;
+ }
+
+ return buflen;
+}
+
static int
smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
{
@@ -277,6 +297,7 @@ smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
struct kvec *iov = rqst->rq_iov;
int n_vec = rqst->rq_nvec;
unsigned int smb_buf_length = get_rfc1002_length(iov[0].iov_base);
+ unsigned long send_length;
unsigned int i;
size_t total_len = 0, sent;
struct socket *ssocket = server->ssocket;
@@ -285,6 +306,14 @@ smb_send_rqst(struct TCP_Server_Info *server, struct smb_rqst *rqst)
if (ssocket == NULL)
return -ENOTSOCK;
+ /* sanity check send length */
+ send_length = rqst_len(rqst);
+ if (send_length != smb_buf_length + 4) {
+ WARN(1, "Send length mismatch(send_length=%lu smb_buf_length=%u)\n",
+ send_length, smb_buf_length);
+ return -EIO;
+ }
+
cifs_dbg(FYI, "Sending smb: smb_len=%u\n", smb_buf_length);
dump_smb(iov[0].iov_base, iov[0].iov_len);
--
1.8.5.3
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Looks right.

Reviewed-by: Pavel Shilovsky <piastry-***@public.gmane.org>