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

[PATCH] 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.

Fixes: 32ae976ed3b5 ("selftests/capabilities: Add tests for capability evolution")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
Found this error through static analysis.
---
 tools/testing/selftests/capabilities/test_execve.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/selftests/capabilities/test_execve.c b/tools/testing/selftests/capabilities/test_execve.c
index 47bad7ddc5bc..de187eff177d 100644
--- a/tools/testing/selftests/capabilities/test_execve.c
+++ b/tools/testing/selftests/capabilities/test_execve.c
@@ -149,6 +149,10 @@ static void copy_fromat_to(int fromfd, const char *fromname, const char *toname)
 		ksft_exit_fail_msg("open copy source - %s\n", strerror(errno));
 
 	int to = open(toname, O_CREAT | O_WRONLY | O_EXCL, 0700);
+	if (to == -1) {
+		close(from);
+		ksft_exit_fail_msg("open copy destination - %s\n", strerror(errno));
+	}
 
 	while (true) {
 		char buf[4096];
-- 
2.25.1

Re: [PATCH] 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 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.

Please improve the change description with an imperative wording.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.10-rc5#n94


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


…
> ---
> Found this error through static analysis.
> ---

* Were any special tools involved?

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

Regards,
Markus

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

[Shuah Khan]

On 6/26/24 01:20, 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.
> 
> Fixes: 32ae976ed3b5 ("selftests/capabilities: Add tests for capability evolution")
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>
> ---
> Found this error through static analysis.

Please add this line to change adding details about the tool you used
to find this problem.

> ---
>   tools/testing/selftests/capabilities/test_execve.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/tools/testing/selftests/capabilities/test_execve.c b/tools/testing/selftests/capabilities/test_execve.c
> index 47bad7ddc5bc..de187eff177d 100644
> --- a/tools/testing/selftests/capabilities/test_execve.c
> +++ b/tools/testing/selftests/capabilities/test_execve.c
> @@ -149,6 +149,10 @@ static void copy_fromat_to(int fromfd, const char *fromname, const char *toname)
>   		ksft_exit_fail_msg("open copy source - %s\n", strerror(errno));
>   
>   	int to = open(toname, O_CREAT | O_WRONLY | O_EXCL, 0700);
> +	if (to == -1) {

Changing this check to < instead of checking for just -1 can catch
other error returns.

> +		close(from);
> +		ksft_exit_fail_msg("open copy destination - %s\n", strerror(errno));
> +	}
>   
>   	while (true) {
>   		char buf[4096];

thanks,
-- Shuah

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

[Shuah Khan]

On 6/26/24 13:33, Shuah Khan wrote:
> On 6/26/24 01:20, 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.
>>
>> Fixes: 32ae976ed3b5 ("selftests/capabilities: Add tests for capability evolution")
>> Signed-off-by: Ma Ke <make24@iscas.ac.cn>
>> ---
>> Found this error through static analysis.
> 
> Please add this line to change adding details about the tool you used
> to find this problem.
> 
>> ---
>>   tools/testing/selftests/capabilities/test_execve.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/tools/testing/selftests/capabilities/test_execve.c b/tools/testing/selftests/capabilities/test_execve.c
>> index 47bad7ddc5bc..de187eff177d 100644
>> --- a/tools/testing/selftests/capabilities/test_execve.c
>> +++ b/tools/testing/selftests/capabilities/test_execve.c
>> @@ -149,6 +149,10 @@ static void copy_fromat_to(int fromfd, const char *fromname, const char *toname)
>>           ksft_exit_fail_msg("open copy source - %s\n", strerror(errno));
>>       int to = open(toname, O_CREAT | O_WRONLY | O_EXCL, 0700);
>> +    if (to == -1) {
> 
> Changing this check to < instead of checking for just -1 can catch
> other error returns.

While you are fining this, can you fix this as well:

  int from = openat(fromfd, fromname, O_RDONLY);
         if (from == -1)
                 ksft_exit_fail_msg("open copy source - %s\n", strerror(errno));

Same change to check for <

thanks,
-- Shuah