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AJvYcCVWsGz9fX1ueOw4Qkzk2jYUkvt7g45T+7XmVJ9KcPI5jfboUriEQf8qkJper26/y8zU8iRBdwOBrYi5Jw5OllQmIPRk3YyeMDCRC3u4/kaqMrGODm/d1zSwRHFQyM2Jgfsr1bTqchWb3AYd4GfzQeIjiTj0+z6+uRUS X-Gm-Message-State: AOJu0YwmWSEA6ZKpa4AwViZB/zZzNDZjTNgjuRbi1EIq3hVMIC4fl4sJ NuWnUbu0NhgwMNAKilDem5rufldJhMAR15QHUZrR9Nik/Z3fy/EQ X-Google-Smtp-Source: AGHT+IHFhpUsM+UjoIZsvc9abfXBBwVr4Pvy2R6DexEfQuaMWZGPVsyFvMSpNFqyTQepijGjgMqDtw== X-Received: by 2002:a17:903:18d:b0:1fa:f9e1:5d33 with SMTP id d9443c01a7336-1faf9e15e0amr32122215ad.50.1720009322425; Wed, 03 Jul 2024 05:22:02 -0700 (PDT) Received: from localhost.localdomain ([240e:604:203:6020:9d53:3114:91d1:7a47]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fb24fbd598sm3616985ad.199.2024.07.03.05.21.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Jul 2024 05:22:01 -0700 (PDT) From: Fred Li To: pabeni@redhat.com Cc: aleksander.lobakin@intel.com, andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, davem@davemloft.net, dracodingfly@gmail.com, edumazet@google.com, haoluo@google.com, hawk@kernel.org, john.fastabend@gmail.com, jolsa@kernel.org, kpsingh@kernel.org, kuba@kernel.org, linux-kernel@vger.kernel.org, linux@weissschuh.net, martin.lau@linux.dev, mkhalfella@purestorage.com, nbd@nbd.name, netdev@vger.kernel.org, sashal@kernel.org, sdf@google.com, song@kernel.org, yonghong.song@linux.dev, herbert@gondor.apana.org.au Subject: Re: [PATCH v2 1/2] net: Fix skb_segment when splitting gso_size mangled skb having linear-headed frag_list whose head_frag=true Date: Wed, 3 Jul 2024 20:21:53 +0800 Message-Id: <20240703122153.25381-1-dracodingfly@gmail.com> X-Mailer: git-send-email 2.32.1 (Apple Git-133) In-Reply-To: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit > I must admit I more than a bit lost in the many turns of skb_segment(), > but the above does not look like the correct solution, as it will make > the later BUG_ON() unreachable/meaningless. Sorry, the subsequent BUG_ON maybe should be removed in this patch, because for skb_headlen(list_skb) > len, it will continue splitting as commit 13acc94eff122 (net: permit skb_segment on head_frag frag_list skb) does. > > Do I read correctly that when the BUG_ON() triggers: > > list_skb->len is 125 > len is 75 > list_skb->frag_head is true > yes, it's correct. list_skb->len is 125 gso_size is 75, also the len in the BUG_ON conditon list_skb->head_frag is true > It looks like skb_segment() is becoming even and ever more complex to > cope with unexpected skb layouts, only possibly when skb_segment() is > called by some BPF helpers. > > Thanks, > > Paolo I'll wait for more suggestions from others. Thanks Fred Li