Re: [PATCH] mm: Don't let userspace spam allocations warnings

[Kees Cook]

On Wed, Feb 20, 2019 at 12:41 PM Daniel Vetter <daniel.vetter@xxxxxxxx> wrote:
>
> memdump_user usually gets fed unchecked userspace input. Blasting a
> full backtrace into dmesg every time is a bit excessive - I'm not sure
> on the kernel rule in general, but at least in drm we're trying not to
> let unpriviledge userspace spam the logs freely. Definitely not entire
> warning backtraces.
>
> It also means more filtering for our CI, because our testsuite
> exercises these corner cases and so hits these a lot.
>
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>

Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>

-Kees

> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Roman Gushchin <guro@xxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Jan Stancek <jstancek@xxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
> Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
> Cc: Huang Ying <ying.huang@xxxxxxxxx>
> Cc: Bartosz Golaszewski <brgl@xxxxxxxx>
> Cc: linux-mm@xxxxxxxxx
> ---
>  mm/util.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/util.c b/mm/util.c
> index 1ea055138043..379319b1bcfd 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -150,7 +150,7 @@ void *memdup_user(const void __user *src, size_t len)
>  {
>         void *p;
>
> -       p = kmalloc_track_caller(len, GFP_USER);
> +       p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN);
>         if (!p)
>                 return ERR_PTR(-ENOMEM);
>
> --
> 2.20.1
>


-- 
Kees Cook