From aa5d5f8e502318e783545ba5d04bb40130b83e20 Mon Sep 17 00:00:00 2001 From: Natasha Klaus Date: Fri, 9 Oct 2026 16:38:07 +0300 Subject: [PATCH] io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6 io_connect_bpf_populate() fills connect.port and connect.v6_addr for AF_INET6 only when addr_len >= sizeof(struct sockaddr_in6), i.e. 28 bytes. The IPv6 connect paths accept SIN6_LEN_RFC2133 (24 bytes), which already holds sin6_port and sin6_addr. io_connect() passes addr_len to the socket layer unchanged. At addr_len 24 the filter sees family AF_INET6 with port and address zero, while the kernel connects to the real destination. A filter that denies an IPv6 port or address is bypassed. Denying connect.port == P rejects [::1]:P with -EACCES at addr_len 28 but connects at addr_len 24. Use SIN6_LEN_RFC2133 as the threshold. sin6_scope_id stays zero when absent. The threshold mismatch was found by an AI coding assistant (Claude Code) comparing this hook against the net/ipv6 length checks on my instructions; it also drafted the reproducer and this patch. I verified the bypass and the fix in a VM on 7.3-rc6 and that 7.2 has the same code. Fixes: 899bea8248ce ("io_uring/net: allow filtering on IORING_OP_CONNECT") Cc: stable@vger.kernel.org # 7.2 Signed-off-by: Natasha Klaus Link: https://patch.msgid.link/20261009133807.730724-1-natalie.klaus@runtimeverification.com Signed-off-by: Jens Axboe --- io_uring/net.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/io_uring/net.c b/io_uring/net.c index 050ed274170a..f5f4f3ce6ef3 100644 --- a/io_uring/net.c +++ b/io_uring/net.c @@ -7,6 +7,7 @@ #include #include #include +#include #include #include @@ -1741,7 +1742,8 @@ void io_connect_bpf_populate(struct io_uring_bpf_ctx *bctx, struct io_kiocb *req case AF_INET6: { struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)ss; - if (conn->addr_len < (int)sizeof(*sin6)) + /* The IPv6 stack accepts SIN6_LEN_RFC2133; port and addr are in it. */ + if (conn->addr_len < SIN6_LEN_RFC2133) break; bctx->connect.port = sin6->sin6_port; memcpy(bctx->connect.v6_addr, &sin6->sin6_addr,