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

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Message-ID: <CAFqZXNvb2AD6T6NcubAbbzdbNoU1ThZ_P+5ioG844mnEs_9=xA@mail.gmail.com>
Date:   Tue, 14 Jun 2022 16:57:32 +0200
From:   Ondrej Mosnacek <omosnace@...hat.com>
To:     xiujianfeng <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 Tue, Jun 14, 2022 at 3:35 PM xiujianfeng <xiujianfeng@...wei.com> wrote:
>
>
> 在 2022/6/14 20:57, Ondrej Mosnacek 写道:
> > 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?
> No problem, patch already sent.

Wow, you're fast :) Thanks!

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