CVE-2018-20124.patch

From 1b46b0fb7e9830d335676b925e10969ed992ee65 Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Thu, 13 Dec 2018 01:00:34 +0530
Subject: [PATCH] rdma: check num_sge does not exceed MAX_SGE

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>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
---
Rebased from 0e68373c by arzhan.i.kinzhalin@intel.com
---
 hw/rdma/rdma_backend.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/hw/rdma/rdma_backend.c b/hw/rdma/rdma_backend.c
index 5c7b3d8949..6519818d98 100644
--- a/hw/rdma/rdma_backend.c
+++ b/hw/rdma/rdma_backend.c
@@ -49,6 +49,17 @@ static void dummy_comp_handler(int status, unsigned int vendor_err, void *ctx)
     pr_err("No completion handler is registered\n");
 }
 
+static inline void complete_work(enum ibv_wc_status status, uint32_t vendor_err,
+                                 void *ctx)
+{
+    struct ibv_wc wc = {0};
+
+    wc.status = status;
+    wc.vendor_err = vendor_err;
+
+    comp_handler(ctx, &wc);
+}
+
 static void poll_cq(RdmaDeviceResources *rdma_dev_res, struct ibv_cq *ibcq)
 {
     int i, ne;
@@ -264,9 +275,9 @@ 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");
-        comp_handler(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;
     }
 
@@ -343,9 +354,9 @@ 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");
-        comp_handler(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;
     }
 
-- 
2.20.0