linux-kernel - Re: [PATCH 2/4] fs: Remove FIRMWARE_PREALLOC_BUFFER from kernel_read

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <202007101543.912633AA73@keescook>
Date:   Fri, 10 Jul 2020 15:44:06 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Scott Branden <scott.branden@...adcom.com>
Cc:     Matthew Wilcox <willy@...radead.org>,
        James Morris <jmorris@...ei.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Jessica Yu <jeyu@...nel.org>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Casey Schaufler <casey@...aufler-ca.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Matthew Garrett <matthewgarrett@...gle.com>,
        David Howells <dhowells@...hat.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        KP Singh <kpsingh@...gle.com>, Dave Olsthoorn <dave@...aar.me>,
        Hans de Goede <hdegoede@...hat.com>,
        Peter Jones <pjones@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Boyd <stephen.boyd@...aro.org>,
        Paul Moore <paul@...l-moore.com>, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCH 2/4] fs: Remove FIRMWARE_PREALLOC_BUFFER from
 kernel_read_file() enums

On Fri, Jul 10, 2020 at 03:10:25PM -0700, Scott Branden wrote:
> 
> 
> On 2020-07-10 3:04 p.m., Matthew Wilcox wrote:
> > On Fri, Jul 10, 2020 at 02:00:32PM -0700, Scott Branden wrote:
> > > > @@ -950,8 +951,8 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
> > > >    		goto out;
> > > >    	}
> > > > -	if (id != READING_FIRMWARE_PREALLOC_BUFFER)
> > > > -		*buf = vmalloc(i_size);
> > > > +	if (!*buf)
> > > The assumption that *buf is always NULL when id !=
> > > READING_FIRMWARE_PREALLOC_BUFFER doesn't appear to be correct.
> > > I get unhandled page faults due to this change on boot.
> > Did it give you a stack backtrace?
> Yes, but there's no requirement that *buf need to be NULL when calling this
> function.
> To fix my particular crash I added the following locally:
> 
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3989,7 +3989,7 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char
> __user *, uargs, int, flags)
>  {
>      struct load_info info = { };
>      loff_t size;
> -    void *hdr;
> +    void *hdr = NULL;
>      int err;
> 
>      err = may_init_module();
> > 
> 

Thanks for the diagnosis and fix! I haven't had time to cycle back
around to this series yet. Hopefully soon. :)

-- 
Kees Cook