[PATCH v2] selftests/capabilities: Fix possible file leak in copy_fromat_to

[PATCH v2] selftests/capabilities: Fix possible file leak in copy_fromat_to

[Ma Ke]

The open() function returns -1 on error. openat() and open() initialize
'from' and 'to', and only 'from' validated with 'if' statement. If the
initialization of variable 'to' fails, we should better check the value
of 'to' and close 'from' to avoid possible file leak. Improve the checking
of 'from' additionally.

Fixes: 32ae976ed3b5 ("selftests/capabilities: Add tests for capability evolution")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
Changes in v2:
- modified the patch according to suggestions;
- found by customized static analysis tool.
---
 tools/testing/selftests/capabilities/test_execve.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/capabilities/test_execve.c b/tools/testing/selftests/capabilities/test_execve.c
index 47bad7ddc5bc..6406ab6aa1f5 100644
--- a/tools/testing/selftests/capabilities/test_execve.c
+++ b/tools/testing/selftests/capabilities/test_execve.c
@@ -145,10 +145,14 @@ static void chdir_to_tmpfs(void)
 static void copy_fromat_to(int fromfd, const char *fromname, const char *toname)
 {
 	int from = openat(fromfd, fromname, O_RDONLY);
-	if (from == -1)
+	if (from < 0)
 		ksft_exit_fail_msg("open copy source - %s\n", strerror(errno));
 
 	int to = open(toname, O_CREAT | O_WRONLY | O_EXCL, 0700);
+	if (to < 0) {
+		close(from);
+		ksft_exit_fail_msg("open copy destination - %s\n", strerror(errno));
+	}
 
 	while (true) {
 		char buf[4096];
-- 
2.25.1

Re: [PATCH v2] selftests/capabilities: Fix possible file leak in copy_fromat_to

[Markus Elfring]

>                                        … openat() and open() initialize
> 'from' and 'to', and only 'from' validated with 'if' statement.

Why do you find such information helpful?


>                                                                 If the
> initialization of variable 'to' fails,

The variable assignment will usually succeed.
A stored return value would eventually indicate a failed function call.


>                                        we should better check the value
> of 'to' and close 'from' to avoid possible file leak. Improve the checking
> of 'from' additionally.

Please split desired changes into separate update steps.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.10-rc5#n168


How do you think about to use a summary phrase like “Complete error handling
in copy_fromat_to()”?


…
> ---
> Changes in v2:
> - modified the patch according to suggestions;
> - found by customized static analysis tool.
> ---

* Would you like to replace a duplicate marker line by a blank line?

* I would appreciate further information about the applied tool.


Regards,
Markus

Re: [PATCH v2] selftests/capabilities: Fix possible file leak in copy_fromat_to

[Shuah Khan]

On 6/26/24 19:57, Ma Ke wrote:
> The open() function returns -1 on error. openat() and open() initialize
> 'from' and 'to', and only 'from' validated with 'if' statement. If the
> initialization of variable 'to' fails, we should better check the value
> of 'to' and close 'from' to avoid possible file leak. Improve the checking
> of 'from' additionally.
> 
> Fixes: 32ae976ed3b5 ("selftests/capabilities: Add tests for capability evolution")
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>
> ---
> Changes in v2:
> - modified the patch according to suggestions;
> - found by customized static analysis tool.

Care to give more details on this customized static analysis
tool?

> ---
>   tools/testing/selftests/capabilities/test_execve.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/capabilities/test_execve.c b/tools/testing/selftests/capabilities/test_execve.c
> index 47bad7ddc5bc..6406ab6aa1f5 100644
> --- a/tools/testing/selftests/capabilities/test_execve.c
> +++ b/tools/testing/selftests/capabilities/test_execve.c
> @@ -145,10 +145,14 @@ static void chdir_to_tmpfs(void)
>   static void copy_fromat_to(int fromfd, const char *fromname, const char *toname)
>   {
>   	int from = openat(fromfd, fromname, O_RDONLY);
> -	if (from == -1)
> +	if (from < 0)
>   		ksft_exit_fail_msg("open copy source - %s\n", strerror(errno));
>   
>   	int to = open(toname, O_CREAT | O_WRONLY | O_EXCL, 0700);
> +	if (to < 0) {
> +		close(from);
> +		ksft_exit_fail_msg("open copy destination - %s\n", strerror(errno));
> +	}
>   
>   	while (true) {
>   		char buf[4096];

thanks,
-- Shuah