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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= , Jamal Hadi Salim , Jiri Pirko , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, zjamg , stable@vger.kernel.org Subject: [PATCH 2/2] net/sched: sch_cake: check negative transport offset in cake_overhead() Date: Thu, 17 Sep 2026 20:21:53 +0800 Message-ID: <20260917122153.62722-3-ndaugoing@gmail.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260917122153.62722-1-ndaugoing@gmail.com> References: <20260917122153.62722-1-ndaugoing@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In cake_overhead(), the header length up to the transport layer is computed using logic borrowed from qdisc_pkt_len_segs_init(): /* borrowed from qdisc_pkt_len_segs_init() */ if (!skb->encapsulation) hdr_len = skb_transport_offset(skb); else hdr_len = skb_inner_transport_offset(skb); Both skb_transport_offset() and skb_inner_transport_offset() return a signed int, but hdr_len is declared as unsigned int. If an encapsulated or stripped packet has a negative transport offset, hdr_len is converted to a huge positive integer near UINT_MAX. When passed to skb_header_pointer(skb, hdr_len, ...), the signed offset argument in skb_header_pointer() becomes negative, which can lead to an out-of-bounds pointer (skb->data + negative_offset) and an OOB read. Fix this by declaring hdr_len as int and falling back to the standard cake_calc_overhead() calculation if hdr_len is negative. Fixes: a41851bea7bf ("net: account for encap headers in qdisc pkt len") Cc: stable@vger.kernel.org Signed-off-by: zjamg --- net/sched/sch_cake.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/sched/sch_cake.c b/net/sched/sch_cake.c index dc93267029e7..ce9e85f9571e 100644 --- a/net/sched/sch_cake.c +++ b/net/sched/sch_cake.c @@ -1413,10 +1413,11 @@ static u32 cake_calc_overhead(struct cake_sched_data *qd, u32 len, u32 off) static u32 cake_overhead(struct cake_sched_data *q, const struct sk_buff *skb) { const struct skb_shared_info *shinfo = skb_shinfo(skb); - unsigned int hdr_len, last_len = 0; + unsigned int last_len = 0; u32 off = skb_network_offset(skb); u16 segs = qdisc_pkt_segs(skb); u32 len = qdisc_pkt_len(skb); + int hdr_len; WRITE_ONCE(q->avg_netoff, cake_ewma(q->avg_netoff, off << 16, 8)); @@ -1429,6 +1430,9 @@ static u32 cake_overhead(struct cake_sched_data *q, const struct sk_buff *skb) else hdr_len = skb_inner_transport_offset(skb); + if (unlikely(hdr_len < 0)) + return cake_calc_overhead(q, len, off); + /* + transport layer */ if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))) { -- 2.53.0