[PATCH] 9p: validate PDU length

Tomas Bortoli
2018-07-23T16:46:01Z

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 <tomasbortoli@gmail.com>
Reported-by: syzbot+65c6b72f284a39d416b4@syzkaller.appspotmail.com
---
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(-)

diff --git a/net/9p/client.c b/net/9p/client.c
index 18c5271910dc..92240ccf476b 100644
--- a/net/9p/client.c
+++ b/net/9p/client.c
@@ -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.
diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
index 588bf88c3305..65533c437b7f 100644
--- a/net/9p/trans_fd.c
+++ b/net/9p/trans_fd.c
@@ -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;
diff --git a/net/9p/trans_rdma.c b/net/9p/trans_rdma.c
index 3d414acb7015..2649b2ebf961 100644
--- a/net/9p/trans_rdma.c
+++ b/net/9p/trans_rdma.c
@@ -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;
diff --git a/net/9p/trans_virtio.c b/net/9p/trans_virtio.c
index 05006cbb3361..fc6dc9ca86a4 100644
--- a/net/9p/trans_virtio.c
+++ b/net/9p/trans_virtio.c
@@ -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);
+ }
}
}

--
2.11.0