From: Jakub Sitnicki <jakub@cloudflare.com>
To: bpf@vger.kernel.org
Cc: netdev@vger.kernel.org, Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
kernel-team@cloudflare.com, Martin KaFai Lau <kafai@fb.com>,
Ilya Leoshkevich <iii@linux.ibm.com>,
Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>
Subject: [PATCH bpf-next v2 2/3] selftests/bpf: Fix u8 narrow load checks for bpf_sk_lookup remote_port
Date: Sat, 19 Mar 2022 19:33:55 +0100 [thread overview]
Message-ID: <20220319183356.233666-3-jakub@cloudflare.com> (raw)
In-Reply-To: <20220319183356.233666-1-jakub@cloudflare.com>
In commit 9a69e2b385f4 ("bpf: Make remote_port field in struct
bpf_sk_lookup 16-bit wide") ->remote_port field changed from __u32 to
__be16.
However, narrow load tests which exercise 1-byte sized loads from
offsetof(struct bpf_sk_lookup, remote_port) were not adopted to reflect the
change.
As a result, on little-endian we continue testing loads from addresses:
- (__u8 *)&ctx->remote_port + 3
- (__u8 *)&ctx->remote_port + 4
which map to the zero padding following the remote_port field, and don't
break the tests because there is no observable change.
While on big-endian, we observe breakage because tests expect to see zeros
for values loaded from:
- (__u8 *)&ctx->remote_port - 1
- (__u8 *)&ctx->remote_port - 2
Above addresses map to ->remote_ip6 field, which precedes ->remote_port,
and are populated during the bpf_sk_lookup IPv6 tests.
Unsurprisingly, on s390x we observe:
#136/38 sk_lookup/narrow access to ctx v4:OK
#136/39 sk_lookup/narrow access to ctx v6:FAIL
Fix it by removing the checks for 1-byte loads from offsets outside of the
->remote_port field.
Fixes: 9a69e2b385f4 ("bpf: Make remote_port field in struct bpf_sk_lookup 16-bit wide")
Suggested-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
---
tools/testing/selftests/bpf/progs/test_sk_lookup.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/test_sk_lookup.c b/tools/testing/selftests/bpf/progs/test_sk_lookup.c
index bf5b7caefdd0..38b7a1fe67b6 100644
--- a/tools/testing/selftests/bpf/progs/test_sk_lookup.c
+++ b/tools/testing/selftests/bpf/progs/test_sk_lookup.c
@@ -413,8 +413,7 @@ int ctx_narrow_access(struct bpf_sk_lookup *ctx)
/* Narrow loads from remote_port field. Expect SRC_PORT. */
if (LSB(ctx->remote_port, 0) != ((SRC_PORT >> 0) & 0xff) ||
- LSB(ctx->remote_port, 1) != ((SRC_PORT >> 8) & 0xff) ||
- LSB(ctx->remote_port, 2) != 0 || LSB(ctx->remote_port, 3) != 0)
+ LSB(ctx->remote_port, 1) != ((SRC_PORT >> 8) & 0xff))
return SK_DROP;
if (LSW(ctx->remote_port, 0) != SRC_PORT)
return SK_DROP;
--
2.35.1
next prev parent reply other threads:[~2022-03-19 18:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-19 18:33 [PATCH bpf-next v2 0/3] Make 2-byte access to bpf_sk_lookup->remote_port endian-agnostic Jakub Sitnicki
2022-03-19 18:33 ` [PATCH bpf-next v2 1/3] bpf: Treat bpf_sk_lookup remote_port as a 2-byte field Jakub Sitnicki
2022-03-19 18:33 ` Jakub Sitnicki [this message]
2022-03-19 18:33 ` [PATCH bpf-next v2 3/3] selftests/bpf: Fix test for 4-byte load from remote_port on big-endian Jakub Sitnicki
2022-03-21 2:10 ` [PATCH bpf-next v2 0/3] Make 2-byte access to bpf_sk_lookup->remote_port endian-agnostic patchwork-bot+netdevbpf
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