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[195.135.220.15]) by mx.google.com with ESMTPS id d50si807941edb.246.2019.02.20.14.05.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 20 Feb 2019 14:05:12 -0800 (PST) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 56E82B633; Wed, 20 Feb 2019 22:05:12 +0000 (UTC) Date: Wed, 20 Feb 2019 23:05:10 +0100 From: Michal Hocko To: Daniel Vetter Cc: DRI Development , LKML , Daniel Vetter , Andrew Morton , Mike Rapoport , Roman Gushchin , Vlastimil Babka , Jan Stancek , Kees Cook , Andrey Ryabinin , "Michael S. Tsirkin" , Huang Ying , Bartosz Golaszewski , linux-mm@kvack.org Subject: Re: [PATCH] mm: Don't let userspace spam allocations warnings Message-ID: <20190220220510.GE4525@dhcp22.suse.cz> References: <20190220204058.11676-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190220204058.11676-1-daniel.vetter@ffwll.ch> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed 20-02-19 21:40:58, Daniel Vetter 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. Yes, this makes sense to me. This API sounds like an example where returning ENOMEM to the userspace right away is much better than spamming the log for large allocation requests. Smaller allocations simply do not fail and the OOM killer report will be printed regardless of __GFP_NOWARN. > 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 > Cc: Andrew Morton > Cc: Mike Rapoport > Cc: Michal Hocko > Cc: Roman Gushchin > Cc: Vlastimil Babka > Cc: Jan Stancek > Cc: Kees Cook > Cc: Andrey Ryabinin > Cc: "Michael S. Tsirkin" > Cc: Huang Ying > Cc: Bartosz Golaszewski > Cc: linux-mm@kvack.org Acked-by: Michal Hocko > --- > 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 > -- Michal Hocko SUSE Labs