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From:   Kees Cook <keescook@chromium.org>
Date:   Wed, 20 Feb 2019 13:08:30 -0800
Message-ID: <CAGXu5jLCyQYCrJDXB_jN7cSoEYEqK3PKLBXc64XHicnE48V0bQ@mail.gmail.com>
Subject: Re: [PATCH] mm: Don't let userspace spam allocations warnings
To:     Daniel Vetter <daniel.vetter@ffwll.ch>
Cc:     DRI Development <dri-devel@lists.freedesktop.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Daniel Vetter <daniel.vetter@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Michal Hocko <mhocko@suse.com>, Roman Gushchin <guro@fb.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Jan Stancek <jstancek@redhat.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Huang Ying <ying.huang@intel.com>,
        Bartosz Golaszewski <brgl@bgdev.pl>,
        Linux-MM <linux-mm@kvack.org>
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On Wed, Feb 20, 2019 at 12:41 PM Daniel Vetter <daniel.vetter@ffwll.ch> 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@intel.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Roman Gushchin <guro@fb.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Jan Stancek <jstancek@redhat.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Huang Ying <ying.huang@intel.com>
> Cc: Bartosz Golaszewski <brgl@bgdev.pl>
> Cc: linux-mm@kvack.org
> ---
>  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