linux-kernel - Re: [PATCH 07/12] selftests/mm: set -Wno-format-security to avoid uffd build warnings

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Date:   Fri, 2 Jun 2023 12:15:43 +0200
From:   David Hildenbrand <david@...hat.com>
To:     John Hubbard <jhubbard@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Peter Xu <peterx@...hat.com>, Shuah Khan <shuah@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/12] selftests/mm: set -Wno-format-security to avoid
 uffd build warnings

On 02.06.23 03:33, John Hubbard wrote:
> The uffd_test_start() is perhaps a little too elaborate about how it
> dispatches tests, leading to a clang warning that looks roughly like
> this:
> 
> "uffd-unit-tests.c:1198:20: warning: format string is not a string literal
> (potentially insecure) [-Wformat-security] ...note: treat the string as
> an argument to avoid this.
>      uffd_test_start(test_name);
> "
> 
> However, it doesn't seem worth it to rewrite the way uffd_test_start()
> works, given that these tests are already deeply unsafe to begin with.
> 
> Fix this by just disabling the compiler warning, but only for
> uffd-unit-tests.
> 
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
>   tools/testing/selftests/mm/Makefile | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile
> index 23af4633f0f4..473bf1811552 100644
> --- a/tools/testing/selftests/mm/Makefile
> +++ b/tools/testing/selftests/mm/Makefile
> @@ -170,6 +170,8 @@ $(OUTPUT)/ksm_tests: LDLIBS += -lnuma
>   
>   $(OUTPUT)/migration: LDLIBS += -lnuma
>   
> +$(OUTPUT)/uffd-unit-tests: CFLAGS += -Wno-format-security
> +
>   local_config.mk local_config.h: check_config.sh
>   	/bin/sh ./check_config.sh $(CC)
>   

Maybe the following will silence the warning by removing test_name
completely:


---
  tools/testing/selftests/mm/uffd-unit-tests.c | 5 +----
  1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c
index 269c86768a02..15c76ce972be 100644
--- a/tools/testing/selftests/mm/uffd-unit-tests.c
+++ b/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -1149,7 +1149,6 @@ int main(int argc, char *argv[])
  	uffd_test_case_t *test;
  	mem_type_t *mem_type;
  	uffd_test_args_t args;
-	char test_name[128];
  	const char *errmsg;
  	int has_uffd, opt;
  	int i, j;
@@ -1192,10 +1191,8 @@ int main(int argc, char *argv[])
  			mem_type = &mem_types[j];
  			if (!(test->mem_targets & mem_type->mem_flag))
  				continue;
-			snprintf(test_name, sizeof(test_name),
-				 "%s on %s", test->name, mem_type->name);
  
-			uffd_test_start(test_name);
+			uffd_test_start("%s on %s", test->name, mem_type->name);
  			if (!uffd_feature_supported(test)) {
  				uffd_test_skip("feature missing");
  				continue;


Still gives me

Testing register-ioctls on anon... done
Testing register-ioctls on shmem... done
Testing register-ioctls on shmem-private... done
Testing register-ioctls on hugetlb... skipped [reason: memory allocation failed]
Testing register-ioctls on hugetlb-private... skipped [reason: memory allocation failed]
...

-- 
Thanks,

David / dhildenb