linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Sakari Ailus <sakari.ailus@linux.intel.com>
To: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>,
	linux-kernel@vger.kernel.org, Yong Zhi <yong.zhi@intel.com>,
	Bingbu Cao <bingbu.cao@intel.com>,
	Tianshu Qiu <tian.shu.qiu@intel.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-media@vger.kernel.org, linux-staging@lists.linux.dev,
	linux-hardening@vger.kernel.org,
	Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [PATCH v2 1/2] media: staging/intel-ipu3: css: Fix wrong size comparison
Date: Tue, 10 Aug 2021 19:30:30 +0300	[thread overview]
Message-ID: <20210810163030.GJ3@paasikivi.fi.intel.com> (raw)
In-Reply-To: <a5e19508-4d7a-ba63-7ac0-ed2e56bc3bc1@embeddedor.com>

On Tue, Aug 10, 2021 at 11:26:14AM -0500, Gustavo A. R. Silva wrote:
> Hi Sakari,
> 
> Please, see my comments below...
> 
> On 8/10/21 10:18, Sakari Ailus wrote:
> > Hi Gustavo,
> > 
> > Apologies for the delay.
> > 
> > On Mon, Aug 02, 2021 at 08:46:20AM -0500, Gustavo A. R. Silva wrote:
> >> Hi Sakari,
> >>
> >> On 8/2/21 01:05, Sakari Ailus wrote:
> >>> Hi Gustavo,
> >>>
> >>> I missed you already had sent v2...
> >>>
> >>> On Fri, Jul 30, 2021 at 07:08:13AM -0500, Gustavo A. R. Silva wrote:
> >>>> There is a wrong comparison of the total size of the loaded firmware
> >>>> css->fw->size with the size of a pointer to struct imgu_fw_header.
> >>>>
> >>>> Fix this by using the right operand 'struct imgu_fw_header' for
> >>>> sizeof, instead of 'struct imgu_fw_header *' and turn binary_header
> >>>> into a flexible-array member. Also, adjust the relational operator
> >>>> to be '<=' instead of '<', as it seems that the intention of the
> >>>> comparison is to determine if the loaded firmware contains any
> >>>> 'struct imgu_fw_info' items in the binary_header[] array than merely
> >>>> the file_header (struct imgu_fw_bi_file_h).
> >>>>
> >>>> The replacement of the one-element array with a flexible-array member
> >>>> also help with the ongoing efforts to globally enable -Warray-bounds
> >>>> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> >>>> on memcpy().
> >>>>
> >>>> Link: https://github.com/KSPP/linux/issues/79
> >>>> Link: https://github.com/KSPP/linux/issues/109
> >>>> Fixes: 09d290f0ba21 ("media: staging/intel-ipu3: css: Add support for firmware management")
> >>>> Cc: stable@vger.kernel.org
> >>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> >>>> ---
> >>>>
> >>>> It'd be just great if someone that knows this code better can confirm
> >>>> these changes are correct. In particular the adjustment of the
> >>>> relational operator. Thanks!
> >>>>
> >>>> Changes in v2:
> >>>>  - Use flexible array and adjust relational operator, accordingly.
> >>>
> >>> The operator was just correct. The check is just there to see the firmware
> >>> is at least as large as the struct as which it is being accessed.
> >>
> >> I'm a bit confused, so based on your reply to v1 of this series, this patch
> >> is now correct, right?
> >>
> >> The operator in v1 _was_ correct as long as the one-element array wasn't
> >> transformed into a flexible array, right?
> >>
> >> Notice that generally speaking flexible-array members don't occupy space in the
> >> containing structure:
> >>
> >> $ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
> >> struct imgu_fw_header {
> >> 	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
> >> 	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
> >> 	struct imgu_fw_info        binary_header[] __attribute__((__aligned__(8))); /*    72     0 */
> >>
> >> 	/* size: 72, cachelines: 2, members: 2 */
> >> 	/* forced alignments: 1 */
> >> 	/* last cacheline: 8 bytes */
> >> } __attribute__((__aligned__(8)));
> >>
> >> $ pahole -C imgu_fw_header drivers/staging/media/ipu3/ipu3-css-fw.o
> >> struct imgu_fw_header {
> >> 	struct imgu_fw_bi_file_h   file_header;          /*     0    72 */
> >> 	/* --- cacheline 1 boundary (64 bytes) was 8 bytes ago --- */
> >> 	struct imgu_fw_info        binary_header[1] __attribute__((__aligned__(8))); /*    72  1200 */
> >>
> >> 	/* size: 1272, cachelines: 20, members: 2 */
> >> 	/* forced alignments: 1 */
> >> 	/* last cacheline: 56 bytes */
> >> } __attribute__((__aligned__(8)));
> >>
> >> So, now that the flexible array transformation is included in the same patch as the
> >> bugfix, the operator is changed from '<' to '<='
> > 
> > '<' is correct since you only need as much data as the struct you're about
> > to access is large, not a byte more than that. As Dan noted.
> > 
> > I think you could add a check for binary_nr is at least one.
> 
> If we need to check that binary_nr is at least one, then this would be the right
> change:
> 
>         css->fwp = (struct imgu_fw_header *)css->fw->data;
> -       if (css->fw->size < sizeof(struct imgu_fw_header *) ||
> +       if (css->fw->size < struct_size(css->fwp, binary_header, 1) ||
>             css->fwp->file_header.h_size != sizeof(struct imgu_fw_bi_file_h))
>                 goto bad_fw;

There's already a check the space required for the array of binary_nr is
there. But not the number itself.

-- 
Sakari Ailus

  reply	other threads:[~2021-08-10 16:30 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-30 12:07 [PATCH v2 0/2] Fix size comparison bug and use flexible array Gustavo A. R. Silva
2021-07-30 12:08 ` [PATCH v2 1/2] media: staging/intel-ipu3: css: Fix wrong size comparison Gustavo A. R. Silva
2021-08-02  6:05   ` Sakari Ailus
2021-08-02 13:46     ` Gustavo A. R. Silva
2021-08-04 12:37       ` Dan Carpenter
2021-08-10 15:18       ` Sakari Ailus
2021-08-10 16:26         ` Gustavo A. R. Silva
2021-08-10 16:30           ` Sakari Ailus [this message]
2021-08-10 16:40             ` Gustavo A. R. Silva
2021-07-30 12:09 ` [PATCH v2 2/2] media: staging/intel-ipu3: css: Use the struct_size() helper Gustavo A. R. Silva

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210810163030.GJ3@paasikivi.fi.intel.com \
    --to=sakari.ailus@linux.intel.com \
    --cc=bingbu.cao@intel.com \
    --cc=dan.carpenter@oracle.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=gustavo@embeddedor.com \
    --cc=gustavoars@kernel.org \
    --cc=linux-hardening@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-media@vger.kernel.org \
    --cc=linux-staging@lists.linux.dev \
    --cc=mchehab@kernel.org \
    --cc=tian.shu.qiu@intel.com \
    --cc=yong.zhi@intel.com \
    --subject='Re: [PATCH v2 1/2] media: staging/intel-ipu3: css: Fix wrong size comparison' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).