Re: [PATCH bpf-next] libbpf: Do not require executable permission for shared libraries

[Yonghong Song <yhs@fb.com>]

On 8/6/22 3:20 AM, Hengqi Chen wrote:
> Currently, resolve_full_path() requires executable permission for both
> programs and shared libraries. This causes failures on distos like Debian
> since the shared libraries are not installed executable ([0]). Let's remove
> executable permission check for shared libraries.
> 
>    [0]: https://www.debian.org/doc/debian-policy/

The document is too big. Could you be more specific about
which chapter and copy-paste related statements in the commit message?

> 
> Reported-by: Goro Fuji <goro@fastly.com>
> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> ---
>   tools/lib/bpf/libbpf.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index 77e3797cf75a..f0ce7423afb8 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -10666,7 +10666,7 @@ static const char *arch_specific_lib_paths(void)
>   static int resolve_full_path(const char *file, char *result, size_t result_sz)
>   {
>   	const char *search_paths[3] = {};
> -	int i;
> +	int i, perm = R_OK;
>   
>   	if (str_has_sfx(file, ".so") || strstr(file, ".so.")) {
>   		search_paths[0] = getenv("LD_LIBRARY_PATH");
> @@ -10675,6 +10675,7 @@ static int resolve_full_path(const char *file, char *result, size_t result_sz)
>   	} else {
>   		search_paths[0] = getenv("PATH");
>   		search_paths[1] = "/usr/bin:/usr/sbin";
> +		perm |= X_OK;
>   	}
>   
>   	for (i = 0; i < ARRAY_SIZE(search_paths); i++) {
> @@ -10693,8 +10694,8 @@ static int resolve_full_path(const char *file, char *result, size_t result_sz)
>   			if (!seg_len)
>   				continue;
>   			snprintf(result, result_sz, "%.*s/%s", seg_len, s, file);
> -			/* ensure it is an executable file/link */
> -			if (access(result, R_OK | X_OK) < 0)
> +			/* ensure it has required permissions */
> +			if (access(result, perm) < 0)
>   				continue;
>   			pr_debug("resolved '%s' to '%s'\n", file, result);
>   			return 0;