[PATCH] samples/landlock: fix path_list memory leak

[PATCH] samples/landlock: fix path_list memory leak

[trix]

From: Tom Rix <trix@redhat.com>

Clang static analysis reports this error

sandboxer.c:134:8: warning: Potential leak of memory
  pointed to by 'path_list'
        ret = 0;
              ^
path_list is allocated in parse_path() but never freed.

Signed-off-by: Tom Rix <trix@redhat.com>
---
 samples/landlock/sandboxer.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index 7a15910d2171..4629d011ed61 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -134,6 +134,8 @@ static int populate_ruleset(
 	ret = 0;
 
 out_free_name:
+	if (path_list)
+		free(path_list);
 	free(env_path_name);
 	return ret;
 }
-- 
2.26.3

Re: [PATCH] samples/landlock: fix path_list memory leak

[Nick Desaulniers]

On Tue, Apr 27, 2021 at 11:38 AM <trix@redhat.com> wrote:
>
> From: Tom Rix <trix@redhat.com>
>
> Clang static analysis reports this error
>
> sandboxer.c:134:8: warning: Potential leak of memory
>   pointed to by 'path_list'
>         ret = 0;
>               ^
> path_list is allocated in parse_path() but never freed.
>
> Signed-off-by: Tom Rix <trix@redhat.com>
> ---
>  samples/landlock/sandboxer.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
> index 7a15910d2171..4629d011ed61 100644
> --- a/samples/landlock/sandboxer.c
> +++ b/samples/landlock/sandboxer.c
> @@ -134,6 +134,8 @@ static int populate_ruleset(
>         ret = 0;
>
>  out_free_name:
> +       if (path_list)
> +               free(path_list);

I don't think the conditional is even necessary? By our first `goto
out_free_name;`, `parse_path` has already been called/memory for
`path_list` has already been allocated. `parse_path` doesn't check
whether `malloc` has failed.

>         free(env_path_name);
>         return ret;
>  }
> --
> 2.26.3
>


-- 
Thanks,
~Nick Desaulniers

Re: [PATCH] samples/landlock: fix path_list memory leak

[Mickaël Salaün]

On 27/04/2021 21:13, Nick Desaulniers wrote:
> On Tue, Apr 27, 2021 at 11:38 AM <trix@redhat.com> wrote:
>>
>> From: Tom Rix <trix@redhat.com>
>>
>> Clang static analysis reports this error
>>
>> sandboxer.c:134:8: warning: Potential leak of memory
>>   pointed to by 'path_list'
>>         ret = 0;
>>               ^
>> path_list is allocated in parse_path() but never freed.
>>
>> Signed-off-by: Tom Rix <trix@redhat.com>
>> ---
>>  samples/landlock/sandboxer.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
>> index 7a15910d2171..4629d011ed61 100644
>> --- a/samples/landlock/sandboxer.c
>> +++ b/samples/landlock/sandboxer.c
>> @@ -134,6 +134,8 @@ static int populate_ruleset(
>>         ret = 0;
>>
>>  out_free_name:
>> +       if (path_list)
>> +               free(path_list);
> 
> I don't think the conditional is even necessary? By our first `goto
> out_free_name;`, `parse_path` has already been called/memory for
> `path_list` has already been allocated. `parse_path` doesn't check
> whether `malloc` has failed.

Indeed, no need for the path_list check. In practice, this memory leak
doesn't stay long because of the execve, but I missed this free anyway.
Thanks!

Reviewed-by: Mickaël Salaün <mic@linux.microsoft.com>

> 
>>         free(env_path_name);
>>         return ret;
>>  }
>> --
>> 2.26.3
>>
> 
> 

Re: [PATCH] samples/landlock: fix path_list memory leak

[Tom Rix]

On 4/28/21 2:58 AM, Mickaël Salaün wrote:
> On 27/04/2021 21:13, Nick Desaulniers wrote:
>> On Tue, Apr 27, 2021 at 11:38 AM <trix@redhat.com> wrote:
>>> From: Tom Rix <trix@redhat.com>
>>>
>>> Clang static analysis reports this error
>>>
>>> sandboxer.c:134:8: warning: Potential leak of memory
>>>    pointed to by 'path_list'
>>>          ret = 0;
>>>                ^
>>> path_list is allocated in parse_path() but never freed.
>>>
>>> Signed-off-by: Tom Rix <trix@redhat.com>
>>> ---
>>>   samples/landlock/sandboxer.c | 2 ++
>>>   1 file changed, 2 insertions(+)
>>>
>>> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
>>> index 7a15910d2171..4629d011ed61 100644
>>> --- a/samples/landlock/sandboxer.c
>>> +++ b/samples/landlock/sandboxer.c
>>> @@ -134,6 +134,8 @@ static int populate_ruleset(
>>>          ret = 0;
>>>
>>>   out_free_name:
>>> +       if (path_list)
>>> +               free(path_list);
>> I don't think the conditional is even necessary? By our first `goto
>> out_free_name;`, `parse_path` has already been called/memory for
>> `path_list` has already been allocated. `parse_path` doesn't check
>> whether `malloc` has failed.
> Indeed, no need for the path_list check. In practice, this memory leak
> doesn't stay long because of the execve, but I missed this free anyway.
> Thanks!

Ok, the general problem of not checking if malloc and friends succeeds 
is a different problem.

So remove the check and keep the free ?

Tom

> Reviewed-by: Mickaël Salaün <mic@linux.microsoft.com>
>
>>>          free(env_path_name);
>>>          return ret;
>>>   }
>>> --
>>> 2.26.3
>>>
>>

Re: [PATCH] samples/landlock: fix path_list memory leak

[Mickaël Salaün]

On 28/04/2021 17:36, Tom Rix wrote:
> 
> On 4/28/21 2:58 AM, Mickaël Salaün wrote:
>> On 27/04/2021 21:13, Nick Desaulniers wrote:
>>> On Tue, Apr 27, 2021 at 11:38 AM <trix@redhat.com> wrote:
>>>> From: Tom Rix <trix@redhat.com>
>>>>
>>>> Clang static analysis reports this error
>>>>
>>>> sandboxer.c:134:8: warning: Potential leak of memory
>>>>    pointed to by 'path_list'
>>>>          ret = 0;
>>>>                ^
>>>> path_list is allocated in parse_path() but never freed.
>>>>
>>>> Signed-off-by: Tom Rix <trix@redhat.com>
>>>> ---
>>>>   samples/landlock/sandboxer.c | 2 ++
>>>>   1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/samples/landlock/sandboxer.c
>>>> b/samples/landlock/sandboxer.c
>>>> index 7a15910d2171..4629d011ed61 100644
>>>> --- a/samples/landlock/sandboxer.c
>>>> +++ b/samples/landlock/sandboxer.c
>>>> @@ -134,6 +134,8 @@ static int populate_ruleset(
>>>>          ret = 0;
>>>>
>>>>   out_free_name:
>>>> +       if (path_list)
>>>> +               free(path_list);
>>> I don't think the conditional is even necessary? By our first `goto
>>> out_free_name;`, `parse_path` has already been called/memory for
>>> `path_list` has already been allocated. `parse_path` doesn't check
>>> whether `malloc` has failed.
>> Indeed, no need for the path_list check. In practice, this memory leak
>> doesn't stay long because of the execve, but I missed this free anyway.
>> Thanks!
> 
> Ok, the general problem of not checking if malloc and friends succeeds
> is a different problem.
> 
> So remove the check and keep the free ?

Yes please.

> 
> Tom
> 
>> Reviewed-by: Mickaël Salaün <mic@linux.microsoft.com>
>>
>>>>          free(env_path_name);
>>>>          return ret;
>>>>   }
>>>> -- 
>>>> 2.26.3
>>>>
>>>
>