linux-kernel - Re: [PATCH] samples/landlock: fix path

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Message-ID: <6108e69b-0470-cd71-e477-ba64641cbf58@digikod.net>
Date:   Wed, 28 Apr 2021 11:58:59 +0200
From:   Mickaël Salaün <mic@...ikod.net>
To:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        linux-security-module@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        James Morris <jmorris@...ei.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] samples/landlock: fix path_list memory leak


On 27/04/2021 21:13, Nick Desaulniers wrote:
> On Tue, Apr 27, 2021 at 11:38 AM <trix@...hat.com> wrote:
>>
>> From: Tom Rix <trix@...hat.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@...hat.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@...ux.microsoft.com>

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