optee: check shm reference are consistent in offset/size

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 <[email protected]> Signed-off-by: Etienne Carriere <[email protected]> Reviewed-by: Jens Wiklander <[email protected]>
linaro-swg · Apr 23, 2018 · f5d5641 · f5d5641
1 parent 94c2f2e
commit f5d5641
Showing 1 changed file with 11 additions and 0 deletions.
diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
@@ -284,6 +284,17 @@ 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;