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.

Andrey Ignatov committed 6 years ago

Commit 7aebfa11 parent 6a098153 files · +9 −10Browse files

Unified · Split

3 files

include/uapi/linux/bpf.h +1 −1
net/core/filter.c +7 −8
tools/include/uapi/linux/bpf.h +1 −1

include/uapi/linux/bpf.h+1−1

@@ -3728,7 +3728,7 @@ struct bpf_sock_addr { · 3727 unmodified lines
3728	3728	__u32 user_ip6[4]; /* Allows 1,2,4,8-byte read and 4,8-byte write.
3729	3729	* Stored in network byte order.
3730	3730	*/
3731		− __u32 user_port; /* Allows 4-byte read and write.
	3731	+ __u32 user_port; /* Allows 1,2,4-byte read and 4-byte write.
3732	3732	* Stored in network byte order
3733	3733	*/
3734	3734	__u32 family; /* Allows 4-byte read, but no write */

net/core/filter.c+7−8

@@ -7029,6 +7029,7 @@ static bool sock_addr_is_valid_access(int off, int size, · 7028 unmodified lines
7029	7029	case bpf_ctx_range(struct bpf_sock_addr, msg_src_ip4):
7030	7030	case bpf_ctx_range_till(struct bpf_sock_addr, msg_src_ip6[0],
7031	7031	msg_src_ip6[3]):
	7032	+ case bpf_ctx_range(struct bpf_sock_addr, user_port):
7032	7033	if (type == BPF_READ) {
7033	7034	bpf_ctx_record_field_size(info, size_default);
7034	7035
@@ -7059,10 +7060,6 @@ static bool sock_addr_is_valid_access(int off, int size, · 24 unmodified lines
7059	7060	return false;
7060	7061	}
7061	7062	break;
7062		− case bpf_ctx_range(struct bpf_sock_addr, user_port):
7063		− if (size != size_default)
7064		− return false;
7065		− break;
7066	7063	case offsetof(struct bpf_sock_addr, sk):
7067	7064	if (type != BPF_READ)
7068	7065	return false;
@@ -7958,8 +7955,8 @@ static u32 sock_addr_convert_ctx_access(enum bpf_access_type type, · 889 unmodified lines
7958	7955	struct bpf_insn *insn_buf,
7959	7956	struct bpf_prog prog, u32 target_size)
7960	7957	{
	7958	+ int off, port_size = sizeof_field(struct sockaddr_in6, sin6_port);
7961	7959	struct bpf_insn *insn = insn_buf;
7962		− int off;
7963	7960
7964	7961	switch (si->off) {
7965	7962	case offsetof(struct bpf_sock_addr, user_family):
@@ -7994,9 +7991,11 @@ static u32 sock_addr_convert_ctx_access(enum bpf_access_type type, · 28 unmodified lines
7994	7991	offsetof(struct sockaddr_in6, sin6_port));
7995	7992	BUILD_BUG_ON(sizeof_field(struct sockaddr_in, sin_port) !=
7996	7993	sizeof_field(struct sockaddr_in6, sin6_port));
7997		− SOCK_ADDR_LOAD_OR_STORE_NESTED_FIELD(struct bpf_sock_addr_kern,
7998		− struct sockaddr_in6, uaddr,
7999		− sin6_port, tmp_reg);
	7994	+ /* Account for sin6_port being smaller than user_port. */
	7995	+ port_size = min(port_size, BPF_LDST_BYTES(si));
	7996	+ SOCK_ADDR_LOAD_OR_STORE_NESTED_FIELD_SIZE_OFF(
	7997	+ struct bpf_sock_addr_kern, struct sockaddr_in6, uaddr,
	7998	+ sin6_port, bytes_to_bpf_size(port_size), 0, tmp_reg);
8000	7999	break;
8001	8000
8002	8001	case offsetof(struct bpf_sock_addr, family):

tools/include/uapi/linux/bpf.h+1−1

@@ -3728,7 +3728,7 @@ struct bpf_sock_addr { · 3727 unmodified lines
3728	3728	__u32 user_ip6[4]; /* Allows 1,2,4,8-byte read and 4,8-byte write.
3729	3729	* Stored in network byte order.
3730	3730	*/
3731		− __u32 user_port; /* Allows 4-byte read and write.
	3731	+ __u32 user_port; /* Allows 1,2,4-byte read and 4-byte write.
3732	3732	* Stored in network byte order
3733	3733	*/
3734	3734	__u32 family; /* Allows 4-byte read, but no write */

bpf: Support narrow loads from bpf_sock_addr.user_port

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