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bpf: Make remote_port field in struct bpf_sk_lookup 16-bit wide

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remote_port is another case of a BPF context field documented as a 32-bit
value in network byte order for which the BPF context access converter
generates a load of a zero-padded 16-bit integer in network byte order.

First such case was dst_port in bpf_sock which got addressed in commit
4421a58271 ("bpf: Make dst_port field in struct bpf_sock 16-bit wide").

Loading 4-bytes from the remote_port offset and converting the value with
bpf_ntohl() leads to surprising results, as the expected value is shifted
by 16 bits.

Reduce the confusion by splitting the field in two - a 16-bit field holding
a big-endian integer, and a 16-bit zero-padding anonymous field that
follows it.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220209184333.654927-2-jakub@cloudflare.com
This commit is contained in:
Jakub Sitnicki 2022-02-09 19:43:32 +01:00 committed by Alexei Starovoitov
parent dc37dc617f
commit 9a69e2b385
3 changed files with 6 additions and 4 deletions
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3
include/uapi/linux/bpf.h
View File

@ -6453,7 +6453,8 @@ struct bpf_sk_lookup {
__u32 protocol; /* IP protocol (IPPROTO_TCP, IPPROTO_UDP) */
__u32 remote_ip4; /* Network byte order */
__u32 remote_ip6[4]; /* Network byte order */
__u32 remote_port; /* Network byte order */
__be16 remote_port; /* Network byte order */
__u16 :16; /* Zero padding */
__u32 local_ip4; /* Network byte order */
__u32 local_ip6[4]; /* Network byte order */
__u32 local_port; /* Host byte order */

4
net/bpf/test_run.c
View File

@ -1147,7 +1147,7 @@ int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, const union bpf_attr *kat
if (!range_is_zero(user_ctx, offsetofend(typeof(*user_ctx), local_port), sizeof(*user_ctx)))
goto out;
if (user_ctx->local_port > U16_MAX || user_ctx->remote_port > U16_MAX) {
if (user_ctx->local_port > U16_MAX) {
ret = -ERANGE;
goto out;
}
@ -1155,7 +1155,7 @@ int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, const union bpf_attr *kat
ctx.family = (u16)user_ctx->family;
ctx.protocol = (u16)user_ctx->protocol;
ctx.dport = (u16)user_ctx->local_port;
ctx.sport = (__force __be16)user_ctx->remote_port;
ctx.sport = user_ctx->remote_port;
switch (ctx.family) {
case AF_INET:

3
net/core/filter.c
View File

@ -10843,7 +10843,8 @@ static bool sk_lookup_is_valid_access(int off, int size,
case bpf_ctx_range(struct bpf_sk_lookup, local_ip4):
case bpf_ctx_range_till(struct bpf_sk_lookup, remote_ip6[0], remote_ip6[3]):
case bpf_ctx_range_till(struct bpf_sk_lookup, local_ip6[0], local_ip6[3]):
case bpf_ctx_range(struct bpf_sk_lookup, remote_port):
case offsetof(struct bpf_sk_lookup, remote_port) ...
offsetof(struct bpf_sk_lookup, local_ip4) - 1:
case bpf_ctx_range(struct bpf_sk_lookup, local_port):
case bpf_ctx_range(struct bpf_sk_lookup, ingress_ifindex):
bpf_ctx_record_field_size(info, sizeof(__u32));