On Tue, Jan 26, 2021 at 10:36 AM Florent Revest <revest@xxxxxxxxxxxx> wrote:
>
> When migrating from the bpf.h's to the vmlinux.h's definition of struct
> bps_sock, an interesting LLVM behavior happened. LLVM started producing
> two fetches of ctx->sk in the sockops program this means that the
> verifier could not keep track of the NULL-check on ctx->sk. Therefore,
> we need to extract ctx->sk in a variable before checking and
> dereferencing it.
>
> Acked-by: KP Singh <kpsingh@xxxxxxxxxx>
> Signed-off-by: Florent Revest <revest@xxxxxxxxxxxx>
> ---
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> .../testing/selftests/bpf/progs/socket_cookie_prog.c | 11 ++++++-----
> 1 file changed, 6 insertions(+), 5 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/progs/socket_cookie_prog.c b/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
> index 81e84be6f86d..fbd5eaf39720 100644
> --- a/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
> +++ b/tools/testing/selftests/bpf/progs/socket_cookie_prog.c
> @@ -1,12 +1,13 @@
> // SPDX-License-Identifier: GPL-2.0
> // Copyright (c) 2018 Facebook
>
> -#include <linux/bpf.h>
> -#include <sys/socket.h>
> +#include "vmlinux.h"
>
> #include <bpf/bpf_helpers.h>
> #include <bpf/bpf_endian.h>
>
> +#define AF_INET6 10
> +
> struct socket_cookie {
> __u64 cookie_key;
> __u32 cookie_value;
> @@ -41,7 +42,7 @@ int set_cookie(struct bpf_sock_addr *ctx)
> SEC("sockops")
> int update_cookie(struct bpf_sock_ops *ctx)
> {
> - struct bpf_sock *sk;
> + struct bpf_sock *sk = ctx->sk;
> struct socket_cookie *p;
>
> if (ctx->family != AF_INET6)
> @@ -50,10 +51,10 @@ int update_cookie(struct bpf_sock_ops *ctx)
> if (ctx->op != BPF_SOCK_OPS_TCP_CONNECT_CB)
> return 1;
>
> - if (!ctx->sk)
> + if (!sk)
> return 1;
>
> - p = bpf_sk_storage_get(&socket_cookies, ctx->sk, 0, 0);
> + p = bpf_sk_storage_get(&socket_cookies, sk, 0, 0);
> if (!p)
> return 1;
>
> --
> 2.30.0.280.ga3ce27912f-goog
>
