linux-kernel - Re: [PATCH 06/13] fs/kernel_read_file: Remove redundant size argument

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Date:   Tue, 21 Jul 2020 14:50:12 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Scott Branden <scott.branden@...adcom.com>
Cc:     Mimi Zohar <zohar@...ux.ibm.com>,
        Matthew Wilcox <willy@...radead.org>,
        James Morris <jmorris@...ei.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        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>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, selinux@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 06/13] fs/kernel_read_file: Remove redundant size argument

On Tue, Jul 21, 2020 at 02:43:07PM -0700, Scott Branden wrote:
> On 2020-07-17 10:43 a.m., Kees Cook wrote:
> > In preparation for refactoring kernel_read_file*(), remove the redundant
> > "size" argument which is not needed: it can be included in the return
> > code, with callers adjusted. (VFS reads already cannot be larger than
> > INT_MAX.)
> > 
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> > ---
> >   drivers/base/firmware_loader/main.c |  8 ++++----
> >   fs/kernel_read_file.c               | 20 +++++++++-----------
> >   include/linux/kernel_read_file.h    |  8 ++++----
> >   kernel/kexec_file.c                 | 13 ++++++-------
> >   kernel/module.c                     |  7 +++----
> >   security/integrity/digsig.c         |  5 +++--
> >   security/integrity/ima/ima_fs.c     |  5 +++--
> >   7 files changed, 32 insertions(+), 34 deletions(-)
> > 
> > diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
> > index d4a413ea48ce..ea419c7d3d34 100644
> > --- a/drivers/base/firmware_loader/main.c
> > +++ b/drivers/base/firmware_loader/main.c
> > @@ -462,7 +462,7 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
> >   					     size_t in_size,
> >   					     const void *in_buffer))
> >   {
> > -	loff_t size;
> > +	size_t size;
> >   	int i, len;
> >   	int rc = -ENOENT;
> >   	char *path;
> > @@ -494,10 +494,9 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
> >   		fw_priv->size = 0;
> >   		/* load firmware files from the mount namespace of init */
> > -		rc = kernel_read_file_from_path_initns(path, &buffer,
> > -						       &size, msize,
> > +		rc = kernel_read_file_from_path_initns(path, &buffer, msize,
> >   						       READING_FIRMWARE);
> > -		if (rc) {
> > +		if (rc < 0) {
> >   			if (rc != -ENOENT)
> >   				dev_warn(device, "loading %s failed with error %d\n",
> >   					 path, rc);
> > @@ -506,6 +505,7 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
> >   					 path);
> >   			continue;
> >   		}
> > +		size = rc;
> Change fails to return 0.  Need rc = 0; here.

Oh nice; good catch! I'll fix this.

-- 
Kees Cook