[igt-dev] [PATCH i-g-t 1/3] tests/i915/gem_eio: fix uaf

[Gwan-gyeong Mun]

Looks good to me.

Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>

However, the use after free build issue did not occur only with the "$ 
meson build && ninja -C build" build command guided by the igt 
README.md. How did you check it?

Br,

G.G.


On 6/27/22 7:10 PM, Matthew Auld wrote:
> ../tests/i915/gem_eio.c:277:20: warning: pointer ‘ctx’ used after ‘free’ [-Wuse-after-free]
>    277 |         igt_assert(igt_sysfs_printf(ctx->debugfs, "i915_drop_caches",
> ../lib/igt_core.h:667:20: note: in definition of macro ‘igt_assert’
>    667 |         do { if (!(expr)) \
>        |                    ^~~~
> ../tests/i915/gem_eio.c:274:9: note: call to ‘free’ here
>    274 |         free(ctx);
> 
> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> Cc: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
> ---
>   tests/i915/gem_eio.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tests/i915/gem_eio.c b/tests/i915/gem_eio.c
> index 913a21f9..6cbae6eb 100644
> --- a/tests/i915/gem_eio.c
> +++ b/tests/i915/gem_eio.c
> @@ -270,11 +270,11 @@ static void hang_handler(union sigval arg)
>   		  igt_nsec_elapsed(&ctx->delay) / 1000.0);
>   
>   	igt_assert_eq(timer_delete(ctx->timer), 0);
> -	free(ctx);
>   
>   	/* flush any excess work before we start timing our reset */
>   	igt_assert(igt_sysfs_printf(ctx->debugfs, "i915_drop_caches",
>   				    "%d", DROP_RCU));
> +	free(ctx);
>   
>   	igt_nsec_elapsed(ts);
>   	igt_assert(igt_sysfs_printf(dir, "i915_wedged", "%llu", -1ull));
>