Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 23 Apr 2019 15:35:40 +0100
From:   Mel Gorman <mgorman@techsingularity.net>
To:     Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] mm/page_alloc: avoid potential NULL pointer
 dereference
Message-ID: <20190423143540.GQ18914@techsingularity.net>
References: <20190423120806.3503-1-aryabinin@virtuozzo.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-15
Content-Disposition: inline
In-Reply-To: <20190423120806.3503-1-aryabinin@virtuozzo.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Tue, Apr 23, 2019 at 03:08:05PM +0300, Andrey Ryabinin wrote:
> ac.preferred_zoneref->zone passed to alloc_flags_nofragment() can be NULL.
> 'zone' pointer unconditionally derefernced in alloc_flags_nofragment().
> Bail out on NULL zone to avoid potential crash.
> Currently we don't see any crashes only because alloc_flags_nofragment()
> has another bug which allows compiler to optimize away all accesses to
> 'zone'.
> 
> Fixes: 6bb154504f8b ("mm, page_alloc: spread allocations across zones before introducing fragmentation")
> Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>

Acked-by: Mel Gorman <mgorman@techsingularity.net>

-- 
Mel Gorman
SUSE Labs