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

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Message-ID: <4ece80d4-16fe-1938-7eba-2046840881f6@redhat.com>
Date:   Wed, 28 Apr 2021 08:36:27 -0700
From:   Tom Rix <trix@...hat.com>
To:     Mickaël Salaün <mic@...ikod.net>,
        Nick Desaulniers <ndesaulniers@...gle.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 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@...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!

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@...ux.microsoft.com>
>
>>>          free(env_path_name);
>>>          return ret;
>>>   }
>>> --
>>> 2.26.3
>>>
>>