linux-hardening - [PATCH 2/2][next] media: staging/intel-ipu3: css: Replace one-element array and use struct

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Date:   Thu, 29 Jul 2021 18:22:40 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Yong Zhi <yong.zhi@...el.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Bingbu Cao <bingbu.cao@...el.com>,
        Tianshu Qiu <tian.shu.qiu@...el.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-media@...r.kernel.org, linux-staging@...ts.linux.dev,
        linux-hardening@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
Subject: [PATCH 2/2][next] media: staging/intel-ipu3: css: Replace
 one-element array and use struct_size() helper

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@...nel.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) ||
 	    css->fwp->file_header.h_size != sizeof(struct imgu_fw_bi_file_h))
 		goto bad_fw;
-	if (sizeof(struct imgu_fw_bi_file_h) +
-	    css->fwp->file_header.binary_nr * sizeof(struct imgu_fw_info) >
-	    css->fw->size)
+	if (struct_size(css->fwp, binary_header,
+			css->fwp->file_header.binary_nr) > css->fw->size)
 		goto bad_fw;
 
 	dev_info(dev, "loaded firmware version %.64s, %u binaries, %zu bytes\n",
diff --git a/drivers/staging/media/ipu3/ipu3-css-fw.h b/drivers/staging/media/ipu3/ipu3-css-fw.h
index 3c078f15a295..c0bc57fd678a 100644
--- a/drivers/staging/media/ipu3/ipu3-css-fw.h
+++ b/drivers/staging/media/ipu3/ipu3-css-fw.h
@@ -171,7 +171,7 @@ struct imgu_fw_bi_file_h {
 
 struct imgu_fw_header {
 	struct imgu_fw_bi_file_h file_header;
-	struct imgu_fw_info binary_header[1];	/* binary_nr items */
+	struct imgu_fw_info binary_header[];	/* binary_nr items */
 };
 
 /******************* Firmware functions *******************/
-- 
2.27.0