| From 9a69e2b385f443f244a7e8b8bcafe5ccfb0866b4 Mon Sep 17 00:00:00 2001 |
| From: Jakub Sitnicki <jakub@cloudflare.com> |
| Date: Wed, 9 Feb 2022 19:43:32 +0100 |
| Subject: bpf: Make remote_port field in struct bpf_sk_lookup 16-bit wide |
| |
| From: Jakub Sitnicki <jakub@cloudflare.com> |
| |
| commit 9a69e2b385f443f244a7e8b8bcafe5ccfb0866b4 upstream. |
| |
| 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 |
| 4421a582718a ("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 |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| include/uapi/linux/bpf.h | 3 ++- |
| net/bpf/test_run.c | 4 ++-- |
| net/core/filter.c | 3 ++- |
| 3 files changed, 6 insertions(+), 4 deletions(-) |
| |
| --- a/include/uapi/linux/bpf.h |
| +++ b/include/uapi/linux/bpf.h |
| @@ -6293,7 +6293,8 @@ 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 */ |
| --- a/net/bpf/test_run.c |
| +++ b/net/bpf/test_run.c |
| @@ -960,7 +960,7 @@ int bpf_prog_test_run_sk_lookup(struct b |
| 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; |
| } |
| @@ -968,7 +968,7 @@ int bpf_prog_test_run_sk_lookup(struct b |
| 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: |
| --- a/net/core/filter.c |
| +++ b/net/core/filter.c |
| @@ -10563,7 +10563,8 @@ static bool sk_lookup_is_valid_access(in |
| 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): |
| bpf_ctx_record_field_size(info, sizeof(__u32)); |
| return bpf_ctx_narrow_access_ok(off, size, sizeof(__u32)); |