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 18:18:53 +0300 [thread overview]
Message-ID: <20210810151852.GI3@paasikivi.fi.intel.com> (raw)
In-Reply-To: <3c9ac43d-09ca-e5d5-83a8-7b6d23928763@embeddedor.com>
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.
--
Kind regards,
Sakari Ailus
next prev parent reply other threads:[~2021-08-10 15:19 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 [this message]
2021-08-10 16:26 ` Gustavo A. R. Silva
2021-08-10 16:30 ` Sakari Ailus
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
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