Re: [PATCH bpf v2 14/15] selftests/bpf: Check BPFTOOL env var in detect_bpftool_path()

[Alexei Starovoitov]

On Tue, Feb 17, 2026 at 4:31 PM Ihor Solodrai <ihor.solodrai@xxxxxxxxx> wrote:
>
> The bpftool_maps_access and bpftool_metadata tests may fail on BPF CI
> with "command not found", depending on a workflow.
> This happens because detect_bpftool_path() only checks two hardcoded
> relative paths:
>   - ./tools/sbin/bpftool
>   - ../tools/sbin/bpftool
>
> Add support for a BPFTOOL environment variable that allows specifying
> the exact path to the bpftool binary.
>
> Also replace strncpy() with snprintf() for proper null-termination.
>
> Signed-off-by: Ihor Solodrai <ihor.solodrai@xxxxxxxxx>
> ---
>  tools/testing/selftests/bpf/bpftool_helpers.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/bpftool_helpers.c b/tools/testing/selftests/bpf/bpftool_helpers.c
> index a5824945a4a5..d810e73da6c8 100644
> --- a/tools/testing/selftests/bpf/bpftool_helpers.c
> +++ b/tools/testing/selftests/bpf/bpftool_helpers.c
> @@ -1,5 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  #include "bpftool_helpers.h"
> +#include <stdio.h>
>  #include <unistd.h>
>  #include <string.h>
>  #include <stdbool.h>
> @@ -12,13 +13,24 @@
>  static int detect_bpftool_path(char *buffer)
>  {
>         char tmp[BPFTOOL_PATH_MAX_LEN];
> +       const char *env_path;
> +
> +       /* First, check if BPFTOOL environment variable is set */
> +       env_path = getenv("BPFTOOL");
> +       if (env_path && access(env_path, X_OK) == 0) {
> +               snprintf(buffer, BPFTOOL_PATH_MAX_LEN, "%s", env_path);
> +               return 0;
> +       } else if (env_path) {
> +               fprintf(stderr, "bpftool '%s' doesn't exist or is not executable\n", env_path);
> +               return 1;
> +       }
>
>         /* Check default bpftool location (will work if we are running the
>          * default flavor of test_progs)
>          */
>         snprintf(tmp, BPFTOOL_PATH_MAX_LEN, "./%s", BPFTOOL_DEFAULT_PATH);
>         if (access(tmp, X_OK) == 0) {
> -               strncpy(buffer, tmp, BPFTOOL_PATH_MAX_LEN);
> +               snprintf(buffer, BPFTOOL_PATH_MAX_LEN, "%s", tmp);

I guess it's ok for user space, but

git log --oneline|grep "snprintf with strscpy"
ad789a85b163 mm/cma: replace snprintf with strscpy in cma_new_area
674fb053e95d sparc: vio: Replace snprintf with strscpy in vio_create_one
2dfc417414c6 genirq/proc: Replace snprintf with strscpy in register_handler_proc
f46ebb910989 block: Replace snprintf with strscpy in check_partition
b66215e7b780 media: verisilicon: replace snprintf with strscpy+strlcat
a86028f8e3ee staging: most: sound: replace snprintf with strscpy

and many others...
So.. should we introduce strscpy() in selftests/bpf ?