[PATCH bpf] selftests/bpf: Fix a compiler warning in local_storage test

[PATCH bpf] selftests/bpf: Fix a compiler warning in local_storage test

[KP Singh]

Some compilers trigger a warning when tmp_dir_path is allocated
with a fixed size of 64-bytes and used in the following snprintf:

  snprintf(tmp_exec_path, sizeof(tmp_exec_path), "%s/copy_of_rm",
	   tmp_dir_path);

  warning: ‘/copy_of_rm’ directive output may be truncated writing 11
  bytes into a region of size between 1 and 64 [-Wformat-truncation=]

This is because it assumes that tmp_dir_path can be a maximum of 64
bytes long and, therefore, the end-result can get truncated. Fix it by
not using a fixed size in the initialization of tmp_dir_path which
allows the compiler to track actual size of the array better.

Fixes: 2f94ac191846 ("bpf: Update local storage test to check handling of null ptrs")
Signed-off-by: KP Singh <kpsingh@kernel.org>
---
 tools/testing/selftests/bpf/prog_tests/test_local_storage.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/test_local_storage.c b/tools/testing/selftests/bpf/prog_tests/test_local_storage.c
index 3bfcf00c0a67..d2c16eaae367 100644
--- a/tools/testing/selftests/bpf/prog_tests/test_local_storage.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_local_storage.c
@@ -113,7 +113,7 @@ static bool check_syscall_operations(int map_fd, int obj_fd)
 
 void test_test_local_storage(void)
 {
-	char tmp_dir_path[64] = "/tmp/local_storageXXXXXX";
+	char tmp_dir_path[] = "/tmp/local_storageXXXXXX";
 	int err, serv_sk = -1, task_fd = -1, rm_fd = -1;
 	struct local_storage *skel = NULL;
 	char tmp_exec_path[64];
-- 
2.30.0.365.g02bc693789-goog

Re: [PATCH bpf] selftests/bpf: Fix a compiler warning in local_storage test

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (refs/heads/master):

On Tue,  2 Feb 2021 21:37:30 +0000 you wrote:
> Some compilers trigger a warning when tmp_dir_path is allocated
> with a fixed size of 64-bytes and used in the following snprintf:
> 
>   snprintf(tmp_exec_path, sizeof(tmp_exec_path), "%s/copy_of_rm",
> 	   tmp_dir_path);
> 
>   warning: ‘/copy_of_rm’ directive output may be truncated writing 11
>   bytes into a region of size between 1 and 64 [-Wformat-truncation=]
> 
> [...]

Here is the summary with links:
  - [bpf] selftests/bpf: Fix a compiler warning in local_storage test
    https://git.kernel.org/bpf/bpf-next/c/15075bb7228a

You are awesome, thank you!
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