[LTP] [PATCH] shmat() for 0 (or <PAGESIZE with RND flag) has to fail with REMAPs

[Rafael Tinoco]

Please consider From: Rafael David Tinoco <rafael.tinoco@linaro.org>

> On 30 May 2018, at 12:40, Rafael David Tinoco <rafael.tinoco@linaro.org> wrote:
> 
> From: Rafael David Tinoco <rafael.tinoco@canonical.com>
> 
> Fixes: https://github.com/linux-test-project/ltp/issues/319
> 
> According to upstream thread (https://lkml.org/lkml/2018/5/28/2056),
> cve-2017-5669 needs to address the "new" way of handling nil addresses
> for shmat() when used with MAP_FIXED or SHM_REMAP flags.
> 
> - mapping nil-page is OK on lower addresses with MAP_FIXED (or else X11 is broken)
> - mapping nil-page is NOT OK with SHM_REMAP on lower addresses
> 
> Addresses Davidlohr Bueso's comments/changes:
> 
> commit 8f89c007b6de
> Author: Davidlohr Bueso <dave@stgolabs.net>
> Date:   Fri May 25 14:47:30 2018 -0700
> 
>    ipc/shm: fix shmat() nil address after round-down when remapping
> 
> commit a73ab244f0da
> Author: Davidlohr Bueso <dave@stgolabs.net>
> Date:   Fri May 25 14:47:27 2018 -0700
> 
>    Revert "ipc/shm: Fix shmat mmap nil-page protection"
> 
> For previously test made based on:
> 
> commit 95e91b831f87
> Author: Davidlohr Bueso <dave@stgolabs.net>
> Date:   Mon Feb 27 14:28:24 2017 -0800
> 
>    ipc/shm: Fix shmat mmap nil-page protection
> 
> Signed-off-by: Rafael David Tinoco <rafael.tinoco@linaro.org>
> ---
> testcases/cve/cve-2017-5669.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/testcases/cve/cve-2017-5669.c b/testcases/cve/cve-2017-5669.c
> index 1ca598326..16e4d80be 100644
> --- a/testcases/cve/cve-2017-5669.c
> +++ b/testcases/cve/cve-2017-5669.c
> @@ -28,6 +28,9 @@
>  * is just to see if we get an access error or some other unexpected behaviour.
>  *
>  * See commit 95e91b831f (ipc/shm: Fix shmat mmap nil-page protection)
> + * See commit a73ab244f0da (Revert "ipc/shm: Fix shmat mmap nil-page protect...)
> + * See commit 8f89c007b6de (ipc/shm: fix shmat() nil address after round-dow...)
> + * See https://github.com/linux-test-project/ltp/issues/319
>  */
> #include <sys/types.h>
> #include <sys/ipc.h>
> @@ -60,7 +63,11 @@ static void cleanup(void)
> static void run(void)
> {
> 	tst_res(TINFO, "Attempting to attach shared memory to null page");
> -	shm_addr = shmat(shm_id, ((void *)1), SHM_RND);
> +	/*
> +	 * shmat() for 0 (or < PAGESIZE with RND flag) has to fail with REMAPs
> +	 * https://github.com/linux-test-project/ltp/issues/319
> +	 */
> +	shm_addr = shmat(shm_id, ((void *)1), SHM_RND | SHM_REMAP);
> 	if (shm_addr == (void *)-1) {
> 		shm_addr = NULL;
> 		if (errno == EINVAL) {
> -- 
> 2.17.1