tee: check shm references are consistent in offset/size

BugLink: http://bugs.launchpad.net/bugs/1794889
[ 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@nxp.com>
Signed-off-by: Etienne Carriere <etienne.carriere@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
index 58a5009eacc388b45231d747e7d142163f38e627..a548c369579773a5d19914b0f6d5e725bbc55bb7 100644 (file)
--- a/drivers/tee/tee_core.c
+++ b/drivers/tee/tee_core.c
@@ -181,6 +181,17 @@ 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;