tee: check shm references 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 <alexandre.jutras@nxp.com>
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>

diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
index 0124a91c8d7139cd6840cfffeea64adc1cd1825c..dd46b758852aa9ba2866348e6f973da3447b3623 100644 (file)
--- 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;