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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ddc1803813sm12928885ad.82.2026.09.19.14.36.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 14:36:38 -0700 (PDT) From: Hui Peng To: alex.aring@gmail.com, marcel@holtmann.org, luiz.dentz@gmail.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: linux-bluetooth@vger.kernel.org, linux-wpan@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] 6lowpan: add missing pskb_may_pull() checks in IPHC and NHC compression Date: Sat, 19 Sep 2026 21:36:38 +0000 Message-ID: <20260919213638.3314763-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Precedence: bulk X-Mailing-List: linux-bluetooth@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In `lowpan_header_compress()` (`net/6lowpan/iphc.c`) and `lowpan_nhc_do_compression()` (`net/6lowpan/nhc.c`), the transmit compression path reads `ipv6_hdr(skb)` (`sizeof(struct ipv6hdr)`) and the next-header transport header (`nhc->nexthdrlen`, e.g., `sizeof(struct udphdr)`), and then calls `skb_pull(skb, nhc->nexthdrlen)` and `skb_pull(skb, sizeof(struct ipv6hdr))` without verifying via `pskb_may_pull()` that those headers are present in the linear data area of `skb`. When a short or non-linear `ETH_P_IPV6` frame is transmitted over a 6LoWPAN interface (for example, via `AF_PACKET`), `lowpan_header_compress()` and `lowpan_nhc_do_compression()` read past `skb_tail_pointer(skb)` and trigger `BUG_ON(skb->len < skb->data_len)` in `skb_pull()`. Check `pskb_may_pull(skb, sizeof(struct ipv6hdr))` in `lowpan_header_compress()` and `pskb_may_pull(skb, sizeof(struct ipv6hdr) + nhc->nexthdrlen)` in `lowpan_nhc_do_compression()`. Fixes: 8df8c56a5abc ("6lowpan: Moving generic compression code into 6lowpan_iphc.c") Fixes: 92aa7c65d295 ("6lowpan: add generic nhc layer interface") Assisted-by: LLM Signed-off-by: Hui Peng --- net/6lowpan/iphc.c | 3 +++ net/6lowpan/nhc.c | 5 +++++ 2 files changed, 8 insertions(+) diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c index 37eaff3f7b69..b2be70036ee7 100644 --- a/net/6lowpan/iphc.c +++ b/net/6lowpan/iphc.c @@ -1140,6 +1140,9 @@ int lowpan_header_compress(struct sk_buff *skb, const struct net_device *dev, if (skb->protocol != htons(ETH_P_IPV6)) return -EINVAL; + if (!pskb_may_pull(skb, sizeof(struct ipv6hdr))) + return -EINVAL; + hdr = ipv6_hdr(skb); hc_ptr = head + 2; diff --git a/net/6lowpan/nhc.c b/net/6lowpan/nhc.c index a4dde85664f2..a9bf340c090a 100644 --- a/net/6lowpan/nhc.c +++ b/net/6lowpan/nhc.c @@ -79,6 +79,11 @@ int lowpan_nhc_do_compression(struct sk_buff *skb, const struct ipv6hdr *hdr, goto out; } + if (!pskb_may_pull(skb, sizeof(struct ipv6hdr) + nhc->nexthdrlen)) { + ret = -EINVAL; + goto out; + } + /* In the case of RAW sockets the transport header is not set by * the ip6 stack so we must set it ourselves */ -- 2.55.0.1082.g2b9226bbc0-goog