linux-kernel - Re: [PATCH v1] tools:mm:Check mmap based on return values

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Message-ID: <0dc546e5-d164-48ba-b2bf-c83c98e648b4@linuxfoundation.org>
Date: Wed, 21 Aug 2024 20:53:01 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Yang Ruibin <11162571@...o.com>, Andrew Morton
 <akpm@...ux-foundation.org>, Shuah Khan <shuah@...nel.org>,
 linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: opensource.kernel@...o.com, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v1] tools:mm:Check mmap based on return values

On 8/20/24 21:50, Yang Ruibin wrote:
> To correctly detect whether mmap is successful, must use if
> (map_ptr == MAP_FAILED)to avoid incorrectly handling a valid mapping.

Add "Fix mmap() error paths to check for MAP_FAILED" at the end of the
changelog

Change short log to say "selftests:mm: Fix mmap() error paths to check for MAP_FAILED"
selftests is the right subsystem tag for this change.

"Fix" in the short log will make it easier for this change to be picked up by stables.

> 
> Signed-off-by: Yang Ruibin <11162571@...o.com>
> ---
>   tools/testing/selftests/mm/ksm_tests.c     | 2 +-
>   tools/testing/selftests/mm/madv_populate.c | 2 +-
>   tools/testing/selftests/mm/soft-dirty.c    | 2 +-
>   3 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/ksm_tests.c b/tools/testing/selftests/mm/ksm_tests.c
> index b748c48908d9..dad54840f32e 100644
> --- a/tools/testing/selftests/mm/ksm_tests.c
> +++ b/tools/testing/selftests/mm/ksm_tests.c
> @@ -201,7 +201,7 @@ static void  *allocate_memory(void *ptr, int prot, int mapping, char data, size_
>   {
>   	void *map_ptr = mmap(ptr, map_size, PROT_WRITE, mapping, -1, 0);
>   
> -	if (!map_ptr) {
> +	if (map_ptr == MAP_FAILED) {
>   		perror("mmap");

Use ksft_exit_fail_msg("mmap failed\n") to be consistent with the rest.

>   		return NULL;
>   	}
> diff --git a/tools/testing/selftests/mm/madv_populate.c b/tools/testing/selftests/mm/madv_populate.c
> index ef7d911da13e..b89cb83ca5c5 100644
> --- a/tools/testing/selftests/mm/madv_populate.c
> +++ b/tools/testing/selftests/mm/madv_populate.c
> @@ -34,7 +34,7 @@ static void sense_support(void)
>   
>   	addr = mmap(0, pagesize, PROT_READ | PROT_WRITE,
>   		    MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
> -	if (!addr)
> +	if (addr == MAP_FAILED)
>   		ksft_exit_fail_msg("mmap failed\n");
>   
>   	ret = madvise(addr, pagesize, MADV_POPULATE_READ);
> diff --git a/tools/testing/selftests/mm/soft-dirty.c b/tools/testing/selftests/mm/soft-dirty.c
> index bdfa5d085f00..4ccbc053bcce 100644
> --- a/tools/testing/selftests/mm/soft-dirty.c
> +++ b/tools/testing/selftests/mm/soft-dirty.c
> @@ -134,7 +134,7 @@ static void test_mprotect(int pagemap_fd, int pagesize, bool anon)
>   	if (anon) {
>   		map = mmap(NULL, pagesize, PROT_READ|PROT_WRITE,
>   			   MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
> -		if (!map)
> +		if (map == MAP_FAILED)
>   			ksft_exit_fail_msg("anon mmap failed\n");
>   	} else {
>   		test_fd = open(fname, O_RDWR | O_CREAT, 0664);

With the above fixed:

Reviewed-by: Shuah Khan <skhan@...uxfoundation.org>

thanks,
-- Shuah