From ab9d3db5b320a052452b9cd035599ee3c84bbee9 Mon Sep 17 00:00:00 2001
From: Etienne Carriere <etienne.carriere@linaro.org>
Date: Sun, 29 Apr 2018 14:22:29 +0200
Subject: [PATCH] tee: check shm references are consistent in offset/size
Git-commit: ab9d3db5b320a052452b9cd035599ee3c84bbee9
Patch-mainline: v4.17-rc6
References: bsc#1051510

This change prevents userland from referencing TEE shared memory
outside the area initially allocated by its owner. Prior this change an
application could not reference or access memory it did not own but
it could reference memory not explicitly allocated by owner but still
allocated to the owner due to the memory allocation granule.

Reported-by: Alexandre Jutras <alexandre.jutras@nxp.com>
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/tee/tee_core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
index 0124a91c8d71..dd46b758852a 100644
--- a/drivers/tee/tee_core.c
+++ b/drivers/tee/tee_core.c
@@ -238,6 +238,17 @@ static int params_from_user(struct tee_context *ctx, struct tee_param *params,
 			if (IS_ERR(shm))
 				return PTR_ERR(shm);
 
+			/*
+			 * Ensure offset + size does not overflow offset
+			 * and does not overflow the size of the referred
+			 * shared memory object.
+			 */
+			if ((ip.a + ip.b) < ip.a ||
+			    (ip.a + ip.b) > shm->size) {
+				tee_shm_put(shm);
+				return -EINVAL;
+			}
+
 			params[n].u.memref.shm_offs = ip.a;
 			params[n].u.memref.size = ip.b;
 			params[n].u.memref.shm = shm;
-- 
2.18.0