From: Scott Branden <scott.branden@broadcom.com>
To: Mimi Zohar <zohar@linux.ibm.com>,
Christoph Hellwig <hch@infradead.org>,
Luis Chamberlain <mcgrof@kernel.org>
Cc: viro@zeniv.linux.org.uk, gregkh@linuxfoundation.org,
rafael@kernel.org, ebiederm@xmission.com, jeyu@kernel.org,
jmorris@namei.org, keescook@chromium.org, paul@paul-moore.com,
stephen.smalley.work@gmail.com, eparis@parisplace.org,
nayna@linux.ibm.com, dan.carpenter@oracle.com,
skhan@linuxfoundation.org, geert@linux-m68k.org,
tglx@linutronix.de, bauerman@linux.ibm.com, dhowells@redhat.com,
linux-integrity@vger.kernel.org, linux-fsdevel@vger.kernel.org,
kexec@lists.infradead.org, linux-security-module@vger.kernel.org,
selinux@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/3] fs: reduce export usage of kerne_read*() calls
Date: Fri, 22 May 2020 15:24:32 -0700 [thread overview]
Message-ID: <7525ca03-def7-dfe2-80a9-25270cb0ae05@broadcom.com> (raw)
In-Reply-To: <1589805462.5111.107.camel@linux.ibm.com>
Hi Mimi,
On 2020-05-18 5:37 a.m., Mimi Zohar wrote:
> Hi Christoph,
>
> On Sun, 2020-05-17 at 23:22 -0700, Christoph Hellwig wrote:
>> On Fri, May 15, 2020 at 09:29:33PM +0000, Luis Chamberlain wrote:
>>> On Wed, May 13, 2020 at 11:17:36AM -0700, Christoph Hellwig wrote:
>>>> Can you also move kernel_read_* out of fs.h? That header gets pulled
>>>> in just about everywhere and doesn't really need function not related
>>>> to the general fs interface.
>>> Sure, where should I dump these?
>> Maybe a new linux/kernel_read_file.h? Bonus points for a small top
>> of the file comment explaining the point of the interface, which I
>> still don't get :)
> Instead of rolling your own method of having the kernel read a file,
> which requires call specific security hooks, this interface provides a
> single generic set of pre and post security hooks. The
> kernel_read_file_id enumeration permits the security hook to
> differentiate between callers.
>
> To comply with secure and trusted boot concepts, a file cannot be
> accessible to the caller until after it has been measured and/or the
> integrity (hash/signature) appraised.
>
> In some cases, the file was previously read twice, first to measure
> and/or appraise the file and then read again into a buffer for
> use. This interface reads the file into a buffer once, calls the
> generic post security hook, before providing the buffer to the caller.
> (Note using firmware pre-allocated memory might be an issue.)
>
> Partial reading firmware will result in needing to pre-read the entire
> file, most likely on the security pre hook.
The entire file may be very large and not fit into a buffer.
Hence one of the reasons for a partial read of the file.
For security purposes, you need to change your code to limit the amount
of data it reads into a buffer at one time to not consume or run out of
much memory.
>
> Mimi
Scott
next prev parent reply other threads:[~2020-05-22 22:24 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-13 15:21 [PATCH 0/3] fs: reduce export usage of kerne_read*() calls Luis Chamberlain
2020-05-13 15:21 ` [PATCH 1/3] fs: unexport kernel_read_file() Luis Chamberlain
2020-05-13 15:21 ` [PATCH 2/3] security: add symbol namespace for reading file data Luis Chamberlain
2020-05-13 15:40 ` Eric W. Biederman
2020-05-13 16:09 ` Greg KH
2020-05-13 16:16 ` Luis Chamberlain
2020-05-13 16:26 ` Greg KH
2020-05-13 18:07 ` Josh Triplett
2020-05-13 15:21 ` [PATCH 3/3] fs: move kernel_read*() calls to its own symbol namespace Luis Chamberlain
2020-05-13 16:08 ` Greg KH
2020-05-13 18:17 ` [PATCH 0/3] fs: reduce export usage of kerne_read*() calls Christoph Hellwig
2020-05-15 21:29 ` Luis Chamberlain
2020-05-18 6:22 ` Christoph Hellwig
2020-05-18 12:37 ` Mimi Zohar
2020-05-18 15:21 ` Kees Cook
2020-07-29 1:20 ` Luis Chamberlain
2020-05-22 22:24 ` Scott Branden [this message]
2020-05-22 23:04 ` Kees Cook
2020-05-22 23:25 ` Scott Branden
2020-05-24 2:52 ` Mimi Zohar
2020-06-05 18:15 ` Scott Branden
2020-06-05 18:37 ` Mimi Zohar
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