[CVE-2018-5332][T/X/A][SRU][PATCH 1/1] RDS: Heap OOB write in rds_message_alloc_sgs()

[Po-Hsu Lin]

From: Mohamed Ghannam <simo.ghannam at gmail.com>

CVE-2018-5332

When args->nr_local is 0, nr_pages gets also 0 due some size
calculation via rds_rm_size(), which is later used to allocate
pages for DMA, this bug produces a heap Out-Of-Bound write access
to a specific memory region.

Signed-off-by: Mohamed Ghannam <simo.ghannam at gmail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(cherry picked from commit c095508770aebf1b9218e77026e48345d719b17c)
Signed-off-by: Po-Hsu Lin <po-hsu.lin at canonical.com>
---
 net/rds/rdma.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/rds/rdma.c b/net/rds/rdma.c
index 8d3a851..c7b7590 100644
--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -517,6 +517,9 @@ int rds_rdma_extra_size(struct rds_rdma_args *args)
 
 	local_vec = (struct rds_iovec __user *)(unsigned long) args->local_vec_addr;
 
+	if (args->nr_local == 0)
+		return -EINVAL;
+
 	/* figure out the number of pages in the vector */
 	for (i = 0; i < args->nr_local; i++) {
 		if (copy_from_user(&vec, &local_vec[i],
-- 
2.7.4