linux-kernel - Re: [PATCH -next] selinux: Fix memleak in security_read_state

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Message-ID: <CAFqZXNvHB0cftgbK+mScbZbcO71OLpXrBMxWAx1z1eB27mm8Cw@mail.gmail.com>
Date:   Tue, 14 Jun 2022 14:57:29 +0200
From:   Ondrej Mosnacek <omosnace@...hat.com>
To:     Xiu Jianfeng <xiujianfeng@...wei.com>
Cc:     Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Christian Göttsche <cgzones@...glemail.com>,
        michalorzel.eng@...il.com, Austin Kim <austin.kim@....com>,
        SElinux list <selinux@...r.kernel.org>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] selinux: Fix memleak in security_read_state_kernel

On Mon, Jun 13, 2022 at 4:02 PM Xiu Jianfeng <xiujianfeng@...wei.com> wrote:
> In this function, it directly returns the result of __security_read_policy
> without freeing the allocated memory in *data, cause memory leak issue,
> so free the memory if __security_read_policy failed.
>
> Signed-off-by: Xiu Jianfeng <xiujianfeng@...wei.com>
> ---
>  security/selinux/ss/services.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
> index 69b2734311a6..fe5fcf571c56 100644
> --- a/security/selinux/ss/services.c
> +++ b/security/selinux/ss/services.c
> @@ -4048,6 +4048,7 @@ int security_read_policy(struct selinux_state *state,
>  int security_read_state_kernel(struct selinux_state *state,
>                                void **data, size_t *len)
>  {
> +       int err;
>         struct selinux_policy *policy;
>
>         policy = rcu_dereference_protected(
> @@ -4060,5 +4061,11 @@ int security_read_state_kernel(struct selinux_state *state,
>         if (!*data)
>                 return -ENOMEM;
>
> -       return __security_read_policy(policy, *data, len);
> +       err = __security_read_policy(policy, *data, len);
> +       if (err) {
> +               vfree(*data);
> +               *data = NULL;
> +               *len = 0;
> +       }
> +       return err;
>  }
> --
> 2.17.1
>

security_read_policy() defined a few lines above has the same pattern
(just with vmalloc_user() in place of vmalloc()). Would you like to
send another patch to fix that function as well?

-- 
Ondrej Mosnacek
Software Engineer, Linux Security - SELinux kernel
Red Hat, Inc.