[Qemu-devel] [PATCH v1 1/6] rdma: check num_sge does not exceed MAX_SGE

[P J P <ppandit@redhat.com>]

From: Prasad J Pandit <pjp@fedoraproject.org>

rdma back-end has scatter/gather array ibv_sge[MAX_SGE=4] set
to have 4 elements. A guest could send a 'PvrdmaSqWqe' ring element
with 'num_sge' set to > MAX_SGE, which may lead to OOB access issue.
Add check to avoid it.

Reported-by: Saar Amar <saaramar5@gmail.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
---
 hw/rdma/rdma_backend.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Update v1: use new error code VENDOR_ERR_INV_NUM_SGE
  -> https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg02220.html

diff --git a/hw/rdma/rdma_backend.c b/hw/rdma/rdma_backend.c
index ae1e4dcb29..bd4710d16f 100644
--- a/hw/rdma/rdma_backend.c
+++ b/hw/rdma/rdma_backend.c
@@ -476,9 +476,9 @@ void rdma_backend_post_send(RdmaBackendDev *backend_dev,
     }
 
     pr_dbg("num_sge=%d\n", num_sge);
-    if (!num_sge) {
-        pr_dbg("num_sge=0\n");
-        complete_work(IBV_WC_GENERAL_ERR, VENDOR_ERR_NO_SGE, ctx);
+    if (!num_sge || num_sge > MAX_SGE) {
+        pr_dbg("invalid num_sge=%d\n", num_sge);
+        complete_work(IBV_WC_GENERAL_ERR, VENDOR_ERR_INV_NUM_SGE, ctx);
         return;
     }
 
@@ -603,9 +603,9 @@ void rdma_backend_post_recv(RdmaBackendDev *backend_dev,
     }
 
     pr_dbg("num_sge=%d\n", num_sge);
-    if (!num_sge) {
-        pr_dbg("num_sge=0\n");
-        complete_work(IBV_WC_GENERAL_ERR, VENDOR_ERR_NO_SGE, ctx);
+    if (!num_sge || num_sge > MAX_SGE) {
+        pr_dbg("invalid num_sge=%d\n", num_sge);
+        complete_work(IBV_WC_GENERAL_ERR, VENDOR_ERR_INV_NUM_SGE, ctx);
         return;
     }
 
-- 
2.19.2