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Received: from mail.tipi-net.de ([2a03:4000:43:185::1]) by desiato.infradead.org with esmtps (Exim 4.99.5 #2 (Red Hat Linux)) id 1xHGPX-000000004fw-1PjL for linux-arm-kernel@lists.infradead.org; Thu, 15 Oct 2026 08:02:01 +0000 Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 685AFA1544; Thu, 15 Oct 2026 10:01:41 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tipi-net.de; s=dkim; t=1792051306; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:references; bh=lVUttG8iRwcZ+EEkZGFkY8VCO4ZqOKXFF79fwhVmDpU=; b=u2mCl7oyCi8dyZxjmVyFnt8dJgiEPaEMIOtQGIeJPZSatiNCMbd3UKDKNqpes8pwee5u/F lbvZUwDtJIoRyCjQ/+cS3jNdZajXUjYoxOvqPHBqSmlR9BUNcynm2DieqAh4giytIEf2hk CEwrarokbGLOInTIARveF4YGWoW+66ac4BkojHGFTcV8lCZDnywS+oZHmodumC9PcXZoqa IbiLemW1IXQ5T9xu0JwDwPa61Pzc6ENAVMVimKSjQRHtU25i0FoGXF+Fu+X2WaJyFt68gY 94Gh8P+/sVSBhjl1S9eV8VXeuhpqyGzyrpmP2Wq92Uk3tNqbLdWqCGVxCWhfuA== MIME-Version: 1.0 Date: Thu, 15 Oct 2026 10:01:41 +0200 From: Nicolai Buchwitz To: Maxime Chevallier Cc: netdev-bot+sashiko@kernel.org, davem@davemloft.net, edumazet@kernel.org, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, o.rempel@pengutronix.de, andrew+netdev@lunn.ch, mcoquelin.stm32@gmail.com, alexandre.torgue@foss.st.com, Jose.Abreu@synopsys.com, saeedm@nvidia.com, tariqt@nvidia.com, mbloch@nvidia.com, leon@kernel.org, dtatulea@nvidia.com, alazar@nvidia.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH net-next 1/3] net: selftests: use skb_share_check() in the loopback receive hook In-Reply-To: References: <20261007-nb-net-selftest-shared-net-v1-1-458369bfa1ba@tipi-net.de> <179149509090.434549.9918598206439291164@kernel.org> <533b88ce917b59f4f59f52145d2f035f@tipi-net.de> Message-ID: X-Sender: nb@tipi-net.de Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit X-Last-TLS-Session-Version: TLSv1.3 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261015_090159_741952_8A5733A8 X-CRM114-Status: GOOD ( 14.47 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Maxime On 15.10.2026 09:46, Maxime Chevallier wrote: > [...] >>> Could an IPv4 frame that arrives during ethtool -t make the hook read >>> up >>> to about 64 bytes past skb->tail? Examples would be a minimum-size >>> TCP >>> segment or a frame with ihl=15. >>> >>> The over-read seems to stay inside the skb head allocation, because >>> skb_shared_info follows skb->end. If so, the only effect is a >>> possibly >>> wrong selftest result. >> >> The length check is pre-existing, will address that in a follow-up >> patch. > > I'm unsure about this, Can we instead assume that when one is running > the > "ethtool -t" selftests on a machine, they are doing so in some > controlled > conditions ? > > IOW can we take the assumption that we won't get incoming traffic at > the same > time as we run the selftests, and if we do get some and that triggers a > wrong > result, this is expected ? ethtool selftests are very cheap to run, > only a > handful of seconds, and don't require any extra dependency, it doesn't > cost > much to re-run them if something unexpected happens during them. > > ofc. getting a stray frame during the selftests mustn't crash :) > > That's my take on these tests, but feel free to disagree :) Also fine with me. A stray frame just fails the magic check and gets dropped anyway, so the test result doesn't even change... Two patches less to fight with Clashiko over :) Regards Nicolai