Re: [PATCH] selftests/mm: fix resource leaks in child_vmsplice_memcmp_fn

[David Hildenbrand]

On 04.04.23 05:12, Feng Jiang wrote:
> When the function returns, the 'new' and 'old' are not freed
> and the 'fds[]' are not closed, which can lead to resource leaks.
>
> Signed-off-by: Feng Jiang <jiangfeng@xxxxxxxxxx>
> Suggested-by: Ming Xie <xieming@xxxxxxxxxx>
> ---
>   tools/testing/selftests/mm/cow.c | 43 ++++++++++++++++++++++++--------
>   1 file changed, 32 insertions(+), 11 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
> index c0dd2dfca51b..b8aec05d56f4 100644
> --- a/tools/testing/selftests/mm/cow.c
> +++ b/tools/testing/selftests/mm/cow.c
> @@ -193,26 +193,38 @@ static int child_vmsplice_memcmp_fn(char *mem, size_t size,
>   	char *old, *new;
>   	int fds[2];
>   	char buf;
> +	int ret;
>   
>   	old = malloc(size);
>   	new = malloc(size);
> +	if (!old || !new) {
> +		ret = -ENOMEM;
> +		goto free;
> +	}
>   
>   	/* Backup the original content. */
>   	memcpy(old, mem, size);
>   
> -	if (pipe(fds) < 0)
> -		return -errno;
> +	if (pipe(fds) < 0) {
> +		ret = -errno;
> +		goto free;
> +	}
>   
>   	/* Trigger a read-only pin. */
>   	transferred = vmsplice(fds[1], &iov, 1, 0);
> -	if (transferred < 0)
> -		return -errno;
> -	if (transferred == 0)
> -		return -EINVAL;
> +	if (transferred < 0) {
> +		ret = -errno;
> +		goto close_pipe;
> +	} else if (transferred == 0) {
> +		ret = -EINVAL;
> +		goto close_pipe;
> +	}
>   
>   	/* Unmap it from our page tables. */
> -	if (munmap(mem, size) < 0)
> -		return -errno;
> +	if (munmap(mem, size) < 0) {
> +		ret = -errno;
> +		goto close_pipe;
> +	}
>   
>   	/* Wait until the parent modified it. */
>   	write(comm_pipes->child_ready[1], "0", 1);
> @@ -222,11 +234,20 @@ static int child_vmsplice_memcmp_fn(char *mem, size_t size,
>   	/* See if we still read the old values via the pipe. */
>   	for (total = 0; total < transferred; total += cur) {
>   		cur = read(fds[0], new + total, transferred - total);
> -		if (cur < 0)
> -			return -errno;
> +		if (cur < 0) {
> +			ret = -errno;
> +			goto close_pipe;
> +		}
>   	}
>   
> -	return memcmp(old, new, transferred);
> +	ret = memcmp(old, new, transferred);
> +close_pipe:
> +	close(fds[0]);
> +	close(fds[1]);
> +free:
> +	free(old);
> +	free(new);
> +	return ret;
>   }
>   
>   typedef int (*child_fn)(char *mem, size_t size, struct comm_pipes *comm_pipes);

NAK, the whole point of this function is that the child process will 
exit immediately after executing this function, cleaning up automatically.

--
Thanks,

David / dhildenb