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[34.48.4.250]) by smtp.gmail.com with ESMTPSA id 00721157ae682-81fb8acb5f0sm6856507b3.38.2026.07.30.02.22.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jul 2026 02:22:21 -0700 (PDT) Date: Thu, 30 Jul 2026 05:22:21 -0400 From: Willem de Bruijn To: Qihang , netdev@vger.kernel.org Cc: willemdebruijn.kernel@gmail.com, daniel.zahka@gmail.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, horms@kernel.org, stable@vger.kernel.org, Qihang Message-ID: In-Reply-To: <20260730082925.93759-3-q.h.hack.winter@gmail.com> References: <20260730082925.93759-1-q.h.hack.winter@gmail.com> <20260730082925.93759-3-q.h.hack.winter@gmail.com> Subject: Re: [PATCH net v5 2/2] packet: use consistent hard_header_len in TX_RING send path Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Qihang wrote: > tpacket_snd() reads dev->hard_header_len independently for skb > allocation and header construction in tpacket_fill_skb(). Concurrent > netdevice reconfiguration can therefore make the reserved headroom > smaller than the amount later pushed, or make copylen - hard_header_len > negative. > > Snapshot hard_header_len once before processing ring frames and use it > for the frame limit, headroom allocation, copy length, and skb > construction. Pass the snapshot to tpacket_fill_skb(). > > The separate SOCK_DGRAM consistency problem between hard_header_len and > header_ops->create is not addressed here. > > Fixes: 69e3c75f4d54 ("net: TX_RING and packet mmap") > Cc: stable@vger.kernel.org > Signed-off-by: Qihang Reviewed-by: Willem de Bruijn