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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: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/c1e983f4c17573032601d0b2b1f9d1274f24bc16.1589420814.git.rdna@fb.com
This commit is contained in:
Andrey Ignatov 2020-05-13 18:50:27 -07:00 committed by Alexei Starovoitov
parent 6a09815428
commit 7aebfa1b38
3 changed files with 9 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/uapi/linux/bpf.h
View File

@ -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 */

15
net/core/filter.c
View File

@ -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):

2
tools/include/uapi/linux/bpf.h
View File

@ -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 */