[Qemu-devel] [PATCH 1/5] rdma: check that num_sge does not exceed MAX_SGE

[P J P]

From: Prasad J Pandit <address@hidden>

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 <address@hidden>
Signed-off-by: Prasad J Pandit <address@hidden>
---
 hw/rdma/rdma_backend.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/hw/rdma/rdma_backend.c b/hw/rdma/rdma_backend.c
index d7a4bbd91f..0b3b98a94c 100644
--- a/hw/rdma/rdma_backend.c
+++ b/hw/rdma/rdma_backend.c
@@ -311,8 +311,8 @@ 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");
+    if (!num_sge || num_sge > MAX_SGE) {
+        pr_dbg("invalid num_sge=%d\n", num_sge);
         comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_NO_SGE, ctx);
         return;
     }
@@ -390,8 +390,8 @@ 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");
+    if (!num_sge || num_sge > MAX_SGE) {
+        pr_dbg("invalid num_sge=%d\n", num_sge);
         comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_NO_SGE, ctx);
         return;
     }
-- 
2.19.2