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Date:   Fri, 10 Jul 2020 23:04:11 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     Scott Branden <scott.branden@broadcom.com>
Cc:     Kees Cook <keescook@chromium.org>,
        James Morris <jmorris@namei.org>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Jessica Yu <jeyu@kernel.org>,
        Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
        "Serge E. Hallyn" <serge@hallyn.com>,
        Casey Schaufler <casey@schaufler-ca.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Matthew Garrett <matthewgarrett@google.com>,
        David Howells <dhowells@redhat.com>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        KP Singh <kpsingh@google.com>, Dave Olsthoorn <dave@bewaar.me>,
        Hans de Goede <hdegoede@redhat.com>,
        Peter Jones <pjones@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Stephen Boyd <stephen.boyd@linaro.org>,
        Paul Moore <paul@paul-moore.com>, linux-kernel@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org
Subject: Re: [PATCH 2/4] fs: Remove FIRMWARE_PREALLOC_BUFFER from
 kernel_read_file() enums
Message-ID: <20200710220411.GR12769@casper.infradead.org>
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 <3fdb3c53-7471-14d8-ce6a-251d8b660b8a@broadcom.com>
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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?