[PATCH bpf v2] selftests/bpf: Bump path and command buffer sizes in bpftool_helpers.c

[PATCH bpf v2] selftests/bpf: Bump path and command buffer sizes in bpftool_helpers.c

[Ihor Solodrai]

The path length of 64 is way too low in some envirnoments, which leads
to subtle failures due to truncation [1].

Replace BPFTOOL_PATH_MAX_LEN with PATH_MAX, and set
BPFTOOL_FULL_CMD_MAX_LEN to double of PATH_MAX.

[1] https://github.com/libbpf/libbpf/actions/runs/22980753016/job/66719800527

Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
---
 tools/testing/selftests/bpf/bpftool_helpers.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/bpf/bpftool_helpers.c b/tools/testing/selftests/bpf/bpftool_helpers.c
index 929fc257f431..0a2a4f0a2794 100644
--- a/tools/testing/selftests/bpf/bpftool_helpers.c
+++ b/tools/testing/selftests/bpf/bpftool_helpers.c
@@ -2,18 +2,18 @@
 #include <unistd.h>
 #include <string.h>
 #include <stdbool.h>
+#include <limits.h>
 
 #include "bpf_util.h"
 #include "bpftool_helpers.h"
 
-#define BPFTOOL_PATH_MAX_LEN		64
-#define BPFTOOL_FULL_CMD_MAX_LEN	512
+#define BPFTOOL_FULL_CMD_MAX_LEN	(PATH_MAX * 2)
 
 #define BPFTOOL_DEFAULT_PATH		"tools/sbin/bpftool"
 
 static int detect_bpftool_path(char *buffer, size_t size)
 {
-	char tmp[BPFTOOL_PATH_MAX_LEN];
+	char tmp[PATH_MAX];
 	const char *env_path;
 
 	/* First, check if BPFTOOL environment variable is set */
@@ -29,7 +29,7 @@ static int detect_bpftool_path(char *buffer, size_t size)
 	/* 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);
+	snprintf(tmp, sizeof(tmp), "./%s", BPFTOOL_DEFAULT_PATH);
 	if (access(tmp, X_OK) == 0) {
 		strscpy(buffer, tmp, size);
 		return 0;
@@ -38,7 +38,7 @@ static int detect_bpftool_path(char *buffer, size_t size)
 	/* Check alternate bpftool location (will work if we are running a
 	 * specific flavor of test_progs, e.g. cpuv4 or no_alu32)
 	 */
-	snprintf(tmp, BPFTOOL_PATH_MAX_LEN, "../%s", BPFTOOL_DEFAULT_PATH);
+	snprintf(tmp, sizeof(tmp), "../%s", BPFTOOL_DEFAULT_PATH);
 	if (access(tmp, X_OK) == 0) {
 		strscpy(buffer, tmp, size);
 		return 0;
@@ -50,7 +50,7 @@ static int detect_bpftool_path(char *buffer, size_t size)
 
 static int run_command(char *args, char *output_buf, size_t output_max_len)
 {
-	static char bpftool_path[BPFTOOL_PATH_MAX_LEN] = {0};
+	static char bpftool_path[PATH_MAX] = {};
 	bool suppress_output = !(output_buf && output_max_len);
 	char command[BPFTOOL_FULL_CMD_MAX_LEN];
 	FILE *f;
@@ -60,7 +60,7 @@ static int run_command(char *args, char *output_buf, size_t output_max_len)
 	if (bpftool_path[0] == 0 && detect_bpftool_path(bpftool_path, sizeof(bpftool_path)))
 		return 1;
 
-	ret = snprintf(command, BPFTOOL_FULL_CMD_MAX_LEN, "%s %s%s",
+	ret = snprintf(command, sizeof(command), "%s %s%s",
 		       bpftool_path, args,
 		       suppress_output ? " > /dev/null 2>&1" : "");
 
@@ -84,4 +84,3 @@ int get_bpftool_command_output(char *args, char *output_buf, size_t output_max_l
 {
 	return run_command(args, output_buf, output_max_len);
 }
-
-- 
2.53.0

Re: [PATCH bpf v2] selftests/bpf: Bump path and command buffer sizes in bpftool_helpers.c

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Thu, 12 Mar 2026 16:48:20 -0700 you wrote:
> The path length of 64 is way too low in some envirnoments, which leads
> to subtle failures due to truncation [1].
> 
> Replace BPFTOOL_PATH_MAX_LEN with PATH_MAX, and set
> BPFTOOL_FULL_CMD_MAX_LEN to double of PATH_MAX.
> 
> [1] https://github.com/libbpf/libbpf/actions/runs/22980753016/job/66719800527
> 
> [...]

Here is the summary with links:
  - [bpf,v2] selftests/bpf: Bump path and command buffer sizes in bpftool_helpers.c
    https://git.kernel.org/bpf/bpf-next/c/7e2f40ef0a75

You are awesome, thank you!
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