linux-kernel - Re: [PATCH] landlock: Initialize kernel stack variables properly

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Date:   Thu, 4 Nov 2021 20:41:10 +0900
From:   Austin Kim <austindh.kim@...il.com>
To:     Mickaël Salaün <mic@...ikod.net>
Cc:     "Serge E. Hallyn" <serge@...lyn.com>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] landlock: Initialize kernel stack variables properly

2021년 11월 3일 (수) 오후 9:14, Mickaël Salaün <mic@...ikod.net>님이 작성:
>
> Hi Austin,
>
> On 03/11/2021 08:14, Austin Kim wrote:
> > In case kernel stack variables are not initialized properly, there might
> > be a little chance of kernel information disclosure. So it is better for
> > kernel stack variables to be initialized with null characters.
> >
> > Signed-off-by: Austin Kim <austindh.kim@...il.com>
> > ---
> >  security/landlock/syscalls.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
> > index 32396962f04d..50a6f7091428 100644
> > --- a/security/landlock/syscalls.c
> > +++ b/security/landlock/syscalls.c
> > @@ -320,6 +320,8 @@ SYSCALL_DEFINE4(landlock_add_rule,
> >       if (rule_type != LANDLOCK_RULE_PATH_BENEATH)
> >               return -EINVAL;
> >
> > +     memset(&path_beneath_attr, 0, sizeof(path_beneath_attr));
> > +
>
> This memset is already done with the copy_from_user() call just below.
>

It seems that memset() is done inside copy_from_user().
Thanks for feedback.

BR,
Austin Kim

> >       /* Copies raw user space buffer, only one type for now. */
> >       res = copy_from_user(&path_beneath_attr, rule_attr,
> >                       sizeof(path_beneath_attr));
> >