[PATCH 4.16 187/279] tee: check shm references are consistent in offset/size

[Greg Kroah-Hartman]

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Etienne Carriere <etienne.carriere@xxxxxxxxxx>

[ Upstream commit ab9d3db5b320a052452b9cd035599ee3c84bbee9 ]

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@xxxxxxx>
Signed-off-by: Etienne Carriere <etienne.carriere@xxxxxxxxxx>
Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/tee/tee_core.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- a/drivers/tee/tee_core.c
+++ b/drivers/tee/tee_core.c
@@ -238,6 +238,17 @@ static int params_from_user(struct tee_c
 			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;