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[209.85.167.46]) by smtp.gmail.com with ESMTPSA id p17sm1348915lfc.273.2021.01.07.11.47.19 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 07 Jan 2021 11:47:19 -0800 (PST) Received: by mail-lf1-f46.google.com with SMTP id b26so17375882lff.9 for ; Thu, 07 Jan 2021 11:47:19 -0800 (PST) X-Received: by 2002:a2e:3211:: with SMTP id y17mr27794ljy.61.1610048838877; Thu, 07 Jan 2021 11:47:18 -0800 (PST) MIME-Version: 1.0 References: <20201118194838.753436396@linutronix.de> <20201118204007.169209557@linutronix.de> <20210106180132.41dc249d@gandalf.local.home> <20210106174917.3f8ad0d8@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> In-Reply-To: From: Linus Torvalds Date: Thu, 7 Jan 2021 11:47:02 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [BUG] from x86: Support kmap_local() forced debugging To: Willem de Bruijn Cc: Jakub Kicinski , Steven Rostedt , David Miller , Jonathan Lemon , Thomas Gleixner , LKML , "the arch/x86 maintainers" , Christoph Hellwig , Matthew Wilcox , Daniel Vetter , Andrew Morton , Linux-MM , Peter Zijlstra , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Netdev Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 6, 2021 at 8:45 PM Willem de Bruijn wrote: > > But there are three other kmap_atomic callers under net/ that do not > loop at all, so assume non-compound pages. In esp_output_head, > esp6_output_head and skb_seq_read. The first two directly use > skb_page_frag_refill, which can allocate compound (but not > __GFP_HIGHMEM) pages, and the third can be inserted with > netfilter xt_string in the path of tcp transmit skbs, which can also > have compound pages. I think that these could similarly access > data beyond the end of the kmap_atomic mapped page. I'll take > a closer look. Thanks. Note that I have flushed my random one-liner patch from my system, and expect to get a proper fix through the normal networking pulls. And _if_ the networking people feel that my one-liner was the proper fix, you can use it and add my sign-off if you want to, but it really was more of a "this is the quick ugly fix for testing" rather than anything else. Linus