Commit 7aebfa1b authored by Andrey Ignatov's avatar Andrey Ignatov Committed by Alexei Starovoitov
Browse files

bpf: Support narrow loads from bpf_sock_addr.user_port 



bpf_sock_addr.user_port supports only 4-byte load and it leads to ugly
code in BPF programs, like:

	volatile __u32 user_port = ctx->user_port;
	__u16 port = bpf_ntohs(user_port);

Since otherwise clang may optimize the load to be 2-byte and it's
rejected by verifier.

Add support for 1- and 2-byte loads same way as it's supported for other
fields in bpf_sock_addr like user_ip4, msg_src_ip4, etc.

Signed-off-by: default avatarAndrey Ignatov <rdna@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/c1e983f4c17573032601d0b2b1f9d1274f24bc16.1589420814.git.rdna@fb.com
parent 6a098154

include/uapi/linux/bpf.h

+1 −1
Original line number Diff line number Diff line
@@ -3728,7 +3728,7 @@ struct bpf_sock_addr { 
	__u32 user_ip6[4];	/* Allows 1,2,4,8-byte read and 4,8-byte write.

				 * Stored in network byte order.

				 */

	__u32 user_port;	/* Allows 4-byte read and write.

	__u32 user_port;	/* Allows 1,2,4-byte read and 4-byte write.

				 * Stored in network byte order

				 */

	__u32 family;		/* Allows 4-byte read, but no write */

net/core/filter.c

+7 −8
Original line number Diff line number Diff line
@@ -7029,6 +7029,7 @@ static bool sock_addr_is_valid_access(int off, int size, 
	case bpf_ctx_range(struct bpf_sock_addr, msg_src_ip4):

	case bpf_ctx_range_till(struct bpf_sock_addr, msg_src_ip6[0],

				msg_src_ip6[3]):

	case bpf_ctx_range(struct bpf_sock_addr, user_port):

		if (type == BPF_READ) {

			bpf_ctx_record_field_size(info, size_default);
@@ -7059,10 +7060,6 @@ static bool sock_addr_is_valid_access(int off, int size, 
				return false;

		}

		break;

	case bpf_ctx_range(struct bpf_sock_addr, user_port):

		if (size != size_default)

			return false;

		break;

	case offsetof(struct bpf_sock_addr, sk):

		if (type != BPF_READ)

			return false;
@@ -7958,8 +7955,8 @@ static u32 sock_addr_convert_ctx_access(enum bpf_access_type type, 
					struct bpf_insn *insn_buf,

					struct bpf_prog *prog, u32 *target_size)

{

	int off, port_size = sizeof_field(struct sockaddr_in6, sin6_port);

	struct bpf_insn *insn = insn_buf;

	int off;



	switch (si->off) {

	case offsetof(struct bpf_sock_addr, user_family):
@@ -7994,9 +7991,11 @@ static u32 sock_addr_convert_ctx_access(enum bpf_access_type type, 
			     offsetof(struct sockaddr_in6, sin6_port));

		BUILD_BUG_ON(sizeof_field(struct sockaddr_in, sin_port) !=

			     sizeof_field(struct sockaddr_in6, sin6_port));

		SOCK_ADDR_LOAD_OR_STORE_NESTED_FIELD(struct bpf_sock_addr_kern,

						     struct sockaddr_in6, uaddr,

						     sin6_port, tmp_reg);

		/* Account for sin6_port being smaller than user_port. */

		port_size = min(port_size, BPF_LDST_BYTES(si));

		SOCK_ADDR_LOAD_OR_STORE_NESTED_FIELD_SIZE_OFF(

			struct bpf_sock_addr_kern, struct sockaddr_in6, uaddr,

			sin6_port, bytes_to_bpf_size(port_size), 0, tmp_reg);

		break;



	case offsetof(struct bpf_sock_addr, family):

tools/include/uapi/linux/bpf.h

+1 −1
Original line number Diff line number Diff line
@@ -3728,7 +3728,7 @@ struct bpf_sock_addr { 
	__u32 user_ip6[4];	/* Allows 1,2,4,8-byte read and 4,8-byte write.

				 * Stored in network byte order.

				 */

	__u32 user_port;	/* Allows 4-byte read and write.

	__u32 user_port;	/* Allows 1,2,4-byte read and 4-byte write.

				 * Stored in network byte order

				 */

	__u32 family;		/* Allows 4-byte read, but no write */

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