CVE: CVE-2018-20124
Upstream-Status: Backport [https://git.qemu.org/?p=qemu.git;a=commit;h=0e68373]

Backport patch to fix CVE-2018-20124. Update context and stay with current
function comp_handler() which has been replaced with complete_work() in latest
git repo.

Signed-off-by: Kai Kang <kai.kang@windriver.com>

From 0e68373cc2b3a063ce067bc0cc3edaf370752890 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>
---
 hw/rdma/rdma_backend.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/hw/rdma/rdma_backend.c b/hw/rdma/rdma_backend.c
index d7a4bbd9..7f8028f8 100644
--- a/hw/rdma/rdma_backend.c
+++ b/hw/rdma/rdma_backend.c
@@ -311,9 +311,9 @@ 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);
+        comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_NO_SGE, ctx);
         return;
     }
 
@@ -390,9 +390,9 @@ 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);
+        comp_handler(IBV_WC_GENERAL_ERR, VENDOR_ERR_NO_SGE, ctx);
         return;
     }
 
-- 
2.20.1