[PATCH] io_uring/net: allow filtering on IORING_OP_CONNECT

[Shouvik Kar <auxcorelabs@gmail.com>]

This adds custom filtering for IORING_OP_CONNECT, where the target
family is always exposed, and (for AF_INET / AF_INET6) port and
address are exposed. port and v4_addr are in network byte order so
filter authors can compare against on-wire constants.

Skip population unless addr_len covers the populated fields, to
avoid leaking stale io_async_msghdr data on short connects.

Signed-off-by: Shouvik Kar <auxcorelabs@gmail.com>
---
 include/uapi/linux/io_uring/bpf_filter.h | 16 +++++++++
 io_uring/net.c                           | 41 ++++++++++++++++++++++++
 io_uring/net.h                           |  7 ++++
 io_uring/opdef.c                         |  2 ++
 4 files changed, 66 insertions(+)

diff --git a/include/uapi/linux/io_uring/bpf_filter.h b/include/uapi/linux/io_uring/bpf_filter.h
index 1b461d792a7b..ce7d78ab13b3 100644
--- a/include/uapi/linux/io_uring/bpf_filter.h
+++ b/include/uapi/linux/io_uring/bpf_filter.h
@@ -27,6 +27,22 @@ struct io_uring_bpf_ctx {
 			__u64	mode;
 			__u64	resolve;
 		} open;
+		/*
+		 * For CONNECT: fields are populated only when addr_len covers
+		 * them; unpopulated fields are zero from the caller-side memset
+		 * in io_uring_populate_bpf_ctx(). port and v4_addr are network
+		 * byte order. Filters may only issue BPF_LD|BPF_W|BPF_ABS at
+		 * 4-byte aligned offsets; load + mask for sub-word fields.
+		 */
+		struct {
+			__u32	family;	/* sa_family_t zero-extended */
+			__be16	port;
+			__u8	pad[2];
+			union {
+				__be32	v4_addr;
+				__u8	v6_addr[16];
+			};
+		} connect;
 	};
 };
 
diff --git a/io_uring/net.c b/io_uring/net.c
index 30cd22c0b934..cceb5c1409ca 100644
--- a/io_uring/net.c
+++ b/io_uring/net.c
@@ -1674,6 +1674,47 @@ void io_socket_bpf_populate(struct io_uring_bpf_ctx *bctx, struct io_kiocb *req)
 	bctx->socket.protocol = sock->protocol;
 }
 
+void io_connect_bpf_populate(struct io_uring_bpf_ctx *bctx, struct io_kiocb *req)
+{
+	struct io_connect *conn = io_kiocb_to_cmd(req, struct io_connect);
+	struct io_async_msghdr *iomsg = req->async_data;
+	struct sockaddr_storage *ss = &iomsg->addr;
+
+	/*
+	 * move_addr_to_kernel() skips the copy for addr_len == 0, so
+	 * iomsg->addr may hold stale data from a prior CONNECT. Bail
+	 * unless addr_len covers the family discriminator.
+	 */
+	if (conn->addr_len < (int)sizeof(sa_family_t))
+		return;
+
+	bctx->connect.family = ss->ss_family;
+	switch (ss->ss_family) {
+	case AF_INET: {
+		struct sockaddr_in *sin = (struct sockaddr_in *)ss;
+
+		if (conn->addr_len < (int)sizeof(*sin))
+			break;
+		bctx->connect.port = sin->sin_port;
+		bctx->connect.v4_addr = sin->sin_addr.s_addr;
+		break;
+	}
+	case AF_INET6: {
+		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)ss;
+
+		if (conn->addr_len < (int)sizeof(*sin6))
+			break;
+		bctx->connect.port = sin6->sin6_port;
+		memcpy(bctx->connect.v6_addr, &sin6->sin6_addr,
+		       sizeof(bctx->connect.v6_addr));
+		break;
+	}
+	default:
+		/* family is set; per-family fields stay zero - family-only filtering */
+		break;
+	}
+}
+
 int io_socket_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 {
 	struct io_socket *sock = io_kiocb_to_cmd(req, struct io_socket);
diff --git a/io_uring/net.h b/io_uring/net.h
index d4d1ddce50e3..51fda715d3c0 100644
--- a/io_uring/net.h
+++ b/io_uring/net.h
@@ -46,6 +46,7 @@ int io_accept(struct io_kiocb *req, unsigned int issue_flags);
 int io_socket_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_socket(struct io_kiocb *req, unsigned int issue_flags);
 void io_socket_bpf_populate(struct io_uring_bpf_ctx *bctx, struct io_kiocb *req);
+void io_connect_bpf_populate(struct io_uring_bpf_ctx *bctx, struct io_kiocb *req);
 
 int io_connect_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
 int io_connect(struct io_kiocb *req, unsigned int issue_flags);
@@ -69,4 +70,10 @@ static inline void io_socket_bpf_populate(struct io_uring_bpf_ctx *bctx,
 					  struct io_kiocb *req)
 {
 }
+
+static inline void io_connect_bpf_populate(struct io_uring_bpf_ctx *bctx,
+					   struct io_kiocb *req)
+{
+}
+
 #endif
diff --git a/io_uring/opdef.c b/io_uring/opdef.c
index c3ef52b70811..8ea6bd274607 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -203,9 +203,11 @@ const struct io_issue_def io_issue_defs[] = {
 		.unbound_nonreg_file	= 1,
 		.pollout		= 1,
 #if defined(CONFIG_NET)
+		.filter_pdu_size	= sizeof_field(struct io_uring_bpf_ctx, connect),
 		.async_size		= sizeof(struct io_async_msghdr),
 		.prep			= io_connect_prep,
 		.issue			= io_connect,
+		.filter_populate	= io_connect_bpf_populate,
 #else
 		.prep			= io_eopnotsupp_prep,
 #endif
-- 
2.53.0