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Tue, 22 Sep 2026 19:16:40 -0700 (PDT) From: Qihang To: netdev@vger.kernel.org Cc: steffen.klassert@secunet.com, herbert@gondor.apana.org.au, stable@vger.kernel.org, kuba@kernel.org Subject: Re: [PATCH] xfrm: validate ihl in xfrm4_transport_output() Date: Wed, 23 Sep 2026 10:16:35 +0800 Message-ID: <20260923021635.38837-1-q.h.hack.winter@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <178997713210.2160803.14018605703606783403@kernel.org> References: <20260917072226.80788-1-q.h.hack.winter@gmail.com> <178997713210.2160803.14018605703606783403@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Sashiko, Thanks for the review. Both points are valid; I will send a v2. [High] pskb_may_pull() instead of skb->len You are right that skb->len is too loose. __skb_pull() only needs the header to be in the linear area: it BUG()s when the pull drives skb->len below skb->data_len, i.e. when ihl > skb_headlen(skb). skb->len counts the paged fragments too, so an AF_PACKET packet with a virtio net header and hdr_len = 1 leaves skb_headlen() == 1 while skb->len can be large; ihl values up to skb->len then pass the ihl > skb->len check and still reach the BUG() (and the memmove() source runs past skb->tail). v2 uses pskb_may_pull(skb, ihl): it linearizes the header, which both satisfies __skb_pull()'s precondition and keeps the memmove() source in bounds, and it rejects ihl > skb->len. ip_hdr() is re-read afterwards because pskb_may_pull() may reallocate the skb head. [Medium] lower bound on ihl Agreed, thanks. v2 also rejects ihl < 5, matching ip_rcv_core() and the implicit assumption in xfrm4_extract_header() and the IPv4 BEET paths. This keeps the mac_header protocol byte initialized before esp_output() reads it, so the uninitialized-headroom path you described is closed as well. The check is now: if (iph->ihl < 5 || !pskb_may_pull(skb, ihl)) return -EINVAL; iph = ip_hdr(skb); v2 sent separately as [PATCH v2]. pw-bot: cr