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[209.85.217.54]) by smtp.gmail.com with ESMTPSA id o3sm2150105vko.50.2019.04.23.12.17.45 for (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Tue, 23 Apr 2019 12:17:45 -0700 (PDT) Received: by mail-vs1-f54.google.com with SMTP id t23so8945199vso.10 for ; Tue, 23 Apr 2019 12:17:45 -0700 (PDT) X-Received: by 2002:a05:6102:417:: with SMTP id d23mr5177794vsq.48.1556047064431; Tue, 23 Apr 2019 12:17:44 -0700 (PDT) MIME-Version: 1.0 References: <20190418154208.131118-1-glider@google.com> <20190418154208.131118-4-glider@google.com> In-Reply-To: <20190418154208.131118-4-glider@google.com> From: Kees Cook Date: Tue, 23 Apr 2019 12:17:33 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 3/3] RFC: net: apply __GFP_NOINIT to AF_UNIX sk_buff allocations To: Alexander Potapenko Cc: Andrew Morton , Christoph Lameter , Dmitry Vyukov , Laura Abbott , Linux-MM , linux-security-module , Kernel Hardening Content-Type: text/plain; charset="UTF-8" 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 Thu, Apr 18, 2019 at 8:42 AM Alexander Potapenko wrote: > > Add sock_alloc_send_pskb_noinit(), which is similar to > sock_alloc_send_pskb(), but allocates with __GFP_NOINIT. > This helps reduce the slowdown on hackbench from 9% to 0.1%. I would include a detailed justification about why this is safe to do. I imagine (but haven't looked) that the skb is immediately written to after allocation, so this is basically avoiding a "double init". Is that correct? -- Kees Cook