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From: "Gustavo A. R. Silva" <gustavoars@kernel.org>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: linux-kernel@vger.kernel.org, Yong Zhi <yong.zhi@intel.com>,
	Sakari Ailus <sakari.ailus@linux.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
Subject: Re: [PATCH 2/2][next] media: staging/intel-ipu3: css: Replace one-element array and use struct_size() helper
Date: Fri, 30 Jul 2021 03:40:09 -0500	[thread overview]
Message-ID: <20210730084009.GA5422@embeddedor> (raw)
In-Reply-To: <20210730074950.GW1931@kadam>

On Fri, Jul 30, 2021 at 10:49:50AM +0300, Dan Carpenter wrote:
> On Thu, Jul 29, 2021 at 06:22:40PM -0500, Gustavo A. R. Silva wrote:
> > There is a regular need in the kernel to provide a way to declare having
> > a dynamically sized set of trailing elements in a structure. Kernel code
> > should always use “flexible array members”[1] for these cases. The older
> > style of one-element or zero-length arrays should no longer be used[2].
> > 
> > Replace a one-element array with a flexible-array member in struct
> > imgu_fw_header and use the struct_size() helper.
> > 
> > This also helps with the ongoing efforts to globally enable
> > -Warray-bounds and get us closer to being able to tighten the
> > FORTIFY_SOURCE routines on memcpy().
> > 
> > [1] https://en.wikipedia.org/wiki/Flexible_array_member
> > [2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
> > 
> > Link: https://github.com/KSPP/linux/issues/79
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> > ---
> >  drivers/staging/media/ipu3/ipu3-css-fw.c | 5 ++---
> >  drivers/staging/media/ipu3/ipu3-css-fw.h | 2 +-
> >  2 files changed, 3 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/staging/media/ipu3/ipu3-css-fw.c b/drivers/staging/media/ipu3/ipu3-css-fw.c
> > index ab021afff954..3b7df1128840 100644
> > --- a/drivers/staging/media/ipu3/ipu3-css-fw.c
> > +++ b/drivers/staging/media/ipu3/ipu3-css-fw.c
> > @@ -127,9 +127,8 @@ int imgu_css_fw_init(struct imgu_css *css)
> >  	if (css->fw->size < sizeof(struct imgu_fw_header) ||
>                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Originally this was sizeof() the pointer which is clearly wrong.  Then
> patch 1 changed it to force that binary_header[] had at least one
> element, but now it's changed again to say that binary_header[] can have
> zero elements.  So either patch 1 or patch 2 is wrong.
> 
> I feel like the probably the correct fix is to just fold these two
> patches together and say that binary_header[] with zero elements is
> allowed.  But I don't know this code well.

Oops... I forgot to tag this one for stable, too. But it would probably
be better to fold both of these into a single patch as you suggest.

To me these two pieces of code suggest that binary_header[] should not
be declared as a one-element array, but a flexible one instead:

130                 if (sizeof(struct imgu_fw_bi_file_h) +
131                     css->fwp->file_header.binary_nr * sizeof(struct imgu_fw_info) >
132                     css->fw->size)
133                         goto bad_fw;
...
147                 for (i = 0; i < binary_nr; i++) {
148                         struct imgu_fw_info *bi = &css->fwp->binary_header[i];
...

Thanks
--
Gustavo

  reply	other threads:[~2021-07-30  8:37 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29 23:19 [PATCH 0/2][next] Fix size comparison bug and use flexible array Gustavo A. R. Silva
2021-07-29 23:20 ` [PATCH 1/2][next] media: staging/intel-ipu3: css: Fix wrong size comparison Gustavo A. R. Silva
2021-07-29 23:22 ` [PATCH 2/2][next] media: staging/intel-ipu3: css: Replace one-element array and use struct_size() helper Gustavo A. R. Silva
2021-07-30  7:49   ` Dan Carpenter
2021-07-30  8:40     ` Gustavo A. R. Silva [this message]
2021-08-02  6:00       ` Sakari Ailus

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