9p: validate PDU length

PATCH In review Tomas Bortoli 2 participants 4 messages Jul 23, 2018 – Jul 25, 2018

Subsystems (3)

Networking Network drivers 9P file system

lore

Share & tools

lore

Tomas Bortoli

author

2018-07-23 15:44 UTC #0 lore raw

PATCH 1/1 9p: validate PDU length

This commit adds length check for the PDU size.
The size contained in the header has to match the actual size, except for TCP (trans_fd.c) where actual length is not known ahead and the header's length will be checked only against the validity range.

Signed-off-by Tomas Bortoli <[email protected]>

Reported-by [email protected]

---
 net/9p/client.c       | 25 ++++++++++++++++---------
 net/9p/trans_fd.c     |  5 ++++-
 net/9p/trans_rdma.c   |  1 +
 net/9p/trans_virtio.c |  4 +++-
 4 files changed, 24 insertions(+), 11 deletions(-)

net/9p/client.c +16 -9

index 18c5271910dc..92240ccf476b 100644
@@ -477,20 +477,11 @@ p9_parse_header(struct p9_fcall *pdu, int32_t *size, int8_t *type, int16_t *tag,
 	int err;
 
 	pdu->offset = 0;
-	if (pdu->size == 0)
-		pdu->size = 7;
 
 	err = p9pdu_readf(pdu, 0, "dbw", &r_size, &r_type, &r_tag);
 	if (err)
 		goto rewind_and_exit;
 
-	pdu->size = r_size;
-	pdu->id = r_type;
-	pdu->tag = r_tag;
-
-	p9_debug(P9_DEBUG_9P, "<<< size=%d type: %d tag: %d\n",
-		 pdu->size, pdu->id, pdu->tag);
-
 	if (type)
 		*type = r_type;
 	if (tag)

@@ -498,6 +489,16 @@ p9_parse_header(struct p9_fcall *pdu, int32_t *size, int8_t *type, int16_t *tag,
 	if (size)
 		*size = r_size;
 
+	if (pdu->size != r_size || r_size < 7) {
+		err = -EINVAL;
+		goto rewind_and_exit;
+	}
+
+	pdu->id = r_type;
+	pdu->tag = r_tag;
+
+	p9_debug(P9_DEBUG_9P, "<<< size=%d type: %d tag: %d\n",
+		pdu->size, pdu->id, pdu->tag);
 
 rewind_and_exit:
 	if (rewind)

@@ -524,6 +525,12 @@ static int p9_check_errors(struct p9_client *c, struct p9_req_t *req)
 	int ecode;
 
 	err = p9_parse_header(req->rc, NULL, &type, NULL, 0);
+	if (req->rc->size >= c->msize) {
+		p9_debug(P9_DEBUG_ERROR,
+			"requested packet size too big: %d\n",
+			req->rc->size);
+			return -EIO;
+	}
 	/*
 	 * dump the response from server
 	 * This should be after check errors which poplulate pdu_fcall.

net/9p/trans_fd.c +4 -1

index 588bf88c3305..65533c437b7f 100644
@@ -324,7 +324,9 @@ static void p9_read_work(struct work_struct *work)
 	if ((!m->req) && (m->rc.offset == m->rc.capacity)) {
 		p9_debug(P9_DEBUG_TRANS, "got new header\n");
 
-		err = p9_parse_header(&m->rc, NULL, NULL, NULL, 0);
+		/* Header size */
+		m->rc.size = 7;
+		err = p9_parse_header(&m->rc, &m->rc.size, NULL, NULL, 0);
 		if (err) {
 			p9_debug(P9_DEBUG_ERROR,
 				 "error parsing header: %d\n", err);

@@ -369,6 +371,7 @@ static void p9_read_work(struct work_struct *work)
 	 */
 	if ((m->req) && (m->rc.offset == m->rc.capacity)) {
 		p9_debug(P9_DEBUG_TRANS, "got new packet\n");
+		m->req->rc->size = m->rc.offset;
 		spin_lock(&m->client->lock);
 		if (m->req->status != REQ_STATUS_ERROR)
 			status = REQ_STATUS_RCVD;

net/9p/trans_rdma.c +1 -0

index 3d414acb7015..2649b2ebf961 100644
@@ -320,6 +320,7 @@ recv_done(struct ib_cq *cq, struct ib_wc *wc)
 	if (wc->status != IB_WC_SUCCESS)
 		goto err_out;
 
+	c->rc->size = wc->byte_len;
 	err = p9_parse_header(c->rc, NULL, NULL, &tag, 1);
 	if (err)
 		goto err_out;

net/9p/trans_virtio.c +3 -1

index 05006cbb3361..fc6dc9ca86a4 100644
@@ -159,8 +159,10 @@ static void req_done(struct virtqueue *vq)
 		spin_unlock_irqrestore(&chan->lock, flags);
 		/* Wakeup if anyone waiting for VirtIO ring space. */
 		wake_up(chan->vc_wq);
-		if (len)
+		if (len) {
+			req->rc->size = len;
 			p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
+		}
 	}
 }

Signature · 1 line

2.11.0

Dominique Martinet

maintainer

2018-07-24 03:57 UTC #1 lore raw

Tomas Bortoli wrote on Mon, Jul 23, 2018:

Quoted 8 lines

This commit adds length check for the PDU size.
The size contained in the header has to match the actual size, except for TCP (trans_fd.c) where actual length is not known ahead and the header's length will be checked only against the validity range.
Signed-off-by Tomas Bortoli <[email protected]>
Reported-by [email protected]

Ok, I've run some more in-depth testing this time and all appear in order.
Like I said last time, I cannot test the xen transport - if someone can point me to how to set it up or run some tests semi-regularily it'd be great.

Meanwhile, code looks good and appears to work, so I'll take this patch unless someone yells

Quoted 50 lines

---
 net/9p/client.c       | 25 ++++++++++++++++---------
 net/9p/trans_fd.c     |  5 ++++-
 net/9p/trans_rdma.c   |  1 +
 net/9p/trans_virtio.c |  4 +++-
 4 files changed, 24 insertions(+), 11 deletions(-)

net/9p/client.c +10 -9

index 18c5271910dc..92240ccf476b 100644
@@ -477,20 +477,11 @@ p9_parse_header(struct p9_fcall *pdu, int32_t *size, int8_t *type, int16_t *tag,
 	int err;
 
 	pdu->offset = 0;
-	if (pdu->size == 0)
-		pdu->size = 7;
 
 	err = p9pdu_readf(pdu, 0, "dbw", &r_size, &r_type, &r_tag);
 	if (err)
 		goto rewind_and_exit;
 
-	pdu->size = r_size;
-	pdu->id = r_type;
-	pdu->tag = r_tag;
-
-	p9_debug(P9_DEBUG_9P, "<<< size=%d type: %d tag: %d\n",
-		 pdu->size, pdu->id, pdu->tag);
-
 	if (type)
 		*type = r_type;
 	if (tag)

@@ -498,6 +489,16 @@ p9_parse_header(struct p9_fcall *pdu, int32_t *size, int8_t *type, int16_t *tag,
 	if (size)
 		*size = r_size;
 
+	if (pdu->size != r_size || r_size < 7) {
+		err = -EINVAL;
+		goto rewind_and_exit;
+	}
+
+	pdu->id = r_type;
+	pdu->tag = r_tag;
+
+	p9_debug(P9_DEBUG_9P, "<<< size=%d type: %d tag: %d\n",
+		pdu->size, pdu->id, pdu->tag);
 
 rewind_and_exit:
 	if (rewind)

net/9p/client.c static int p9_check_errors(struct p9_client *c, struct p9_req_t *req) · line 532

Quoted 8 lines

net/9p/client.c +5 -0

@@ -524,6 +525,12 @@ static int p9_check_errors(struct p9_client *c, struct p9_req_t *req)
 	int ecode;
 
 	err = p9_parse_header(req->rc, NULL, &type, NULL, 0);
+	if (req->rc->size >= c->msize) {
+		p9_debug(P9_DEBUG_ERROR,
+			"requested packet size too big: %d\n",
+			req->rc->size);
+			return -EIO;

Indentation here looks wrong, I took the liberty of deindenting that return in my tree.

Quoted 55 lines

net/9p/client.c +1 -0

+	}
 	/*
 	 * dump the response from server
 	 * This should be after check errors which poplulate pdu_fcall.

net/9p/trans_fd.c +4 -1

index 588bf88c3305..65533c437b7f 100644
@@ -324,7 +324,9 @@ static void p9_read_work(struct work_struct *work)
 	if ((!m->req) && (m->rc.offset == m->rc.capacity)) {
 		p9_debug(P9_DEBUG_TRANS, "got new header\n");
 
-		err = p9_parse_header(&m->rc, NULL, NULL, NULL, 0);
+		/* Header size */
+		m->rc.size = 7;
+		err = p9_parse_header(&m->rc, &m->rc.size, NULL, NULL, 0);
 		if (err) {
 			p9_debug(P9_DEBUG_ERROR,
 				 "error parsing header: %d\n", err);

@@ -369,6 +371,7 @@ static void p9_read_work(struct work_struct *work)
 	 */
 	if ((m->req) && (m->rc.offset == m->rc.capacity)) {
 		p9_debug(P9_DEBUG_TRANS, "got new packet\n");
+		m->req->rc->size = m->rc.offset;
 		spin_lock(&m->client->lock);
 		if (m->req->status != REQ_STATUS_ERROR)
 			status = REQ_STATUS_RCVD;

net/9p/trans_rdma.c +1 -0

index 3d414acb7015..2649b2ebf961 100644
@@ -320,6 +320,7 @@ recv_done(struct ib_cq *cq, struct ib_wc *wc)
 	if (wc->status != IB_WC_SUCCESS)
 		goto err_out;
 
+	c->rc->size = wc->byte_len;
 	err = p9_parse_header(c->rc, NULL, NULL, &tag, 1);
 	if (err)
 		goto err_out;

net/9p/trans_virtio.c +3 -1

index 05006cbb3361..fc6dc9ca86a4 100644
@@ -159,8 +159,10 @@ static void req_done(struct virtqueue *vq)
 		spin_unlock_irqrestore(&chan->lock, flags);
 		/* Wakeup if anyone waiting for VirtIO ring space. */
 		wake_up(chan->vc_wq);
-		if (len)
+		if (len) {
+			req->rc->size = len;
 			p9_client_cb(chan->client, req, REQ_STATUS_RCVD);
+		}
 	}
 }

Signature · 1 line

Dominique Martinet

Dominique Martinet

maintainer

2018-07-25 04:11 UTC #2 lore raw

In reply to Tomas Bortoli

Tomas Bortoli wrote on Mon, Jul 23, 2018:

net/9p/client.c static int p9_check_errors(struct p9_client *c, struct p9_req_t *req) · line 528

Quoted 9 lines

net/9p/client.c +1 -0

index 18c5271910dc..92240ccf476b 100644
@@ -524,6 +525,12 @@ static int p9_check_errors(struct p9_client *c, struct p9_req_t *req)
 	int ecode;
 
 	err = p9_parse_header(req->rc, NULL, &type, NULL, 0);
+	if (req->rc->size >= c->msize) {

I was looking at this again, I think it's more appropriate to use req->rc->capacity at this point like you did in the first version of the patch.

I had suggested msize in the common p9_parse_header function because that'd let us accept zc requests where the size in the pdu could be bigger than capacity, but this isn't the case in p9_check_errors.

If you're ok with this I'll edit your commit directly, this is less work for me than having to check a new patch.

Thanks,

Signature · 1 line

Dominique

Tomas Bortoli

author

2018-07-25 10:50 UTC #3 lore raw

Quoted 15 lines · Dominique Martinet

Tomas Bortoli wrote on Mon, Jul 23, 2018:
net/9p/client.c static int p9_check_errors(struct p9_client *c, struct p9_req_t *req) · line 528
Quoted 9 lines
net/9p/client.c +1 -0
index 18c5271910dc..92240ccf476b 100644
@@ -524,6 +525,12 @@ static int p9_check_errors(struct p9_client *c, struct p9_req_t *req)
 	int ecode;
 
 	err = p9_parse_header(req->rc, NULL, &type, NULL, 0);
+	if (req->rc->size >= c->msize) {
I was looking at this again, I think it's more appropriate to use req->rc->capacity at this point like you did in the first version of the patch.

Quoted 9 lines

I had suggested msize in the common p9_parse_header function because that'd let us accept zc requests where the size in the pdu could be bigger than capacity, but this isn't the case in p9_check_errors.
If you're ok with this I'll edit your commit directly, this is less work for me than having to check a new patch.
Thanks,

Yes sure, just forward me the changes later.

Tomas