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[34.83.123.78]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-877a95f2abesm1297272b3a.26.2026.09.19.14.06.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Sep 2026 14:06:22 -0700 (PDT) From: Hui Peng To: paul@paul-moore.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: horms@kernel.org, netdev@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] ipv6: calipso: fix 8-bit hdrlen overflow and missing pskb_may_pull() in hop-by-hop options Date: Sat, 19 Sep 2026 21:06:21 +0000 Message-ID: <20260919210621.3029744-1-benquike@gmail.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Precedence: bulk X-Mailing-List: linux-security-module@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Two bugs exist in the CALIPSO hop-by-hop option handling in net/ipv6/calipso.c: 1. When inserting a CALIPSO option into an existing Hop-by-Hop extension header in calipso_opt_insert() or calipso_skbuff_setattr(), the resulting header length `buf_len` (or `ipv6_optlen(hop) + len_delta`) can exceed the maximum size representable by the 8-bit `hdrlen` field (256 * 8 = 2048 bytes). When `buf_len > 2048`, `new->hdrlen = buf_len / 8 - 1` (or `hop->hdrlen = ...`) truncates modulo 256, causing `ipv6_optlen()` to under-report the allocated header size and mismatch `opt->opt_nflen` or `skb->len`. 2. In calipso_skbuff_setattr(), when `ip6_hdr->nexthdr == NEXTHDR_HOP`, `hop` is dereferenced at `(struct ipv6_opt_hdr *)(ip6_hdr + 1)` and scanned by `calipso_opt_find(hop, &start, &end)` without ensuring that the Hop-by-Hop header resides in the linear data area of `skb` via `pskb_may_pull()`, risking an out-of-bounds read past `skb->tail` on non-linear skbs. Reject Hop-by-Hop headers that would exceed `8 * 256` bytes with `-ENOSPC`, and ensure `pskb_may_pull()` linearizes `hop` before inspecting it in calipso_skbuff_setattr(). Fixes: ceba1832b1b2 ("calipso: Set the calipso socket label to match the secattr.") Fixes: 2917f57b6bc1 ("calipso: Allow the lsm to label the skbuff directly.") Assisted-by: LLM Signed-off-by: Hui Peng --- net/ipv6/calipso.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/net/ipv6/calipso.c b/net/ipv6/calipso.c index c6a34334e657..b8b7451a16ed 100644 --- a/net/ipv6/calipso.c +++ b/net/ipv6/calipso.c @@ -944,6 +944,10 @@ calipso_opt_insert(struct ipv6_opt_hdr *hop, memcpy((char *)new + buf_len, (char *)hop + end, hop_len - end); buf_len += hop_len - end; } + if (buf_len > 8 * 256) { + kfree(new); + return ERR_PTR(-ENOSPC); + } new->nexthdr = 0; new->hdrlen = buf_len / 8 - 1; @@ -1323,6 +1327,13 @@ static int calipso_skbuff_setattr(struct sk_buff *skb, ip6_hdr = ipv6_hdr(skb); if (ip6_hdr->nexthdr == NEXTHDR_HOP) { + if (!pskb_may_pull(skb, sizeof(*ip6_hdr) + sizeof(*hop))) + return -EINVAL; + ip6_hdr = ipv6_hdr(skb); + hop = (struct ipv6_opt_hdr *)(ip6_hdr + 1); + if (!pskb_may_pull(skb, sizeof(*ip6_hdr) + ipv6_optlen(hop))) + return -EINVAL; + ip6_hdr = ipv6_hdr(skb); hop = (struct ipv6_opt_hdr *)(ip6_hdr + 1); ret_val = calipso_opt_find(hop, &start, &end); if (ret_val && ret_val != -ENOENT) @@ -1341,6 +1352,8 @@ static int calipso_skbuff_setattr(struct sk_buff *skb, /* At this point new_end aligns to 4n, so (new_end & 4) pads to 8n */ pad = ((new_end & 4) + (end & 7)) & 7; len_delta = new_end - (int)end + pad; + if (start && (int)ipv6_optlen(hop) + len_delta > 8 * 256) + return -ENOSPC; ret_val = skb_cow(skb, skb_headroom(skb) + (len_delta > 0 ? len_delta : 0)); if (ret_val < 0) -- 2.55.0.1082.g2b9226bbc0-goog