linux-kernel - Re: [PATCH] security/selinux: fix potential memleak in error branch

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Message-ID: <CAHC9VhT5ts2Ax+PQ0hV48GzN-xphogfZNSwE97K3-tUZS60BLw@mail.gmail.com>
Date:   Sun, 5 Dec 2021 22:22:56 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Bernard Zhao <bernard@...o.com>
Cc:     Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>, selinux@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] security/selinux: fix potential memleak in error branch

On Wed, Dec 1, 2021 at 10:12 PM Bernard Zhao <bernard@...o.com> wrote:
>
> This patch try to fix potential memleak in error branch.
>
> Signed-off-by: Bernard Zhao <bernard@...o.com>
> ---
>  security/selinux/hooks.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 62d30c0a30c2..10700720bb74 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -983,6 +983,7 @@ static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb,
>  static int selinux_add_opt(int token, const char *s, void **mnt_opts)
>  {
>         struct selinux_mnt_opts *opts = *mnt_opts;
> +       bool is_alloc_opts = false;
>
>         if (token == Opt_seclabel)      /* eaten and completely ignored */
>                 return 0;
> @@ -992,9 +993,13 @@ static int selinux_add_opt(int token, const char *s, void **mnt_opts)
>                 if (!opts)
>                         return -ENOMEM;
>                 *mnt_opts = opts;
> +               is_alloc_opts = true;
>         }
> -       if (!s)
> +       if (!s) {
> +               if (is_alloc_opts)
> +                       kfree(opts);
>                 return -ENOMEM;
> +       }

Thanks for catching this and submitting a patch, but would it be
simpler to do the "(!s)" check before the "(!opts)" check?

>         switch (token) {
>         case Opt_context:
>                 if (opts->context || opts->defcontext)
> @@ -1020,6 +1025,8 @@ static int selinux_add_opt(int token, const char *s, void **mnt_opts)
>         return 0;
>  Einval:
>         pr_warn(SEL_MOUNT_FAIL_MSG);
> +       if (is_alloc_opts)
> +               kfree(opts);
>         return -EINVAL;
>  }
>
> --
> 2.33.1

-- 
paul moore
www.paul-moore.com