linux-kernel - [PATCH v2] mtd: sa1100: avoid VLA in sa1100_setup

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Date:   Mon,  5 Nov 2018 08:58:35 +0100
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        linux-mtd@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        Olof Johansson <olof@...om.net>
Subject: [PATCH v2] mtd: sa1100: avoid VLA in sa1100_setup_mtd

Enabling -Wvla found another variable-length array with randconfig
testing:

drivers/mtd/maps/sa1100-flash.c: In function 'sa1100_setup_mtd':
drivers/mtd/maps/sa1100-flash.c:224:10: error: ISO C90 forbids variable length array 'cdev' [-Werror=vla]

Dynamically allocate the cdev array passed to mtd_concat_create()
instead of using a VLA.

Reported-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Boris Brezillon <boris.brezillon@...tlin.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Olof Johansson <olof@...om.net>
---
Changes in v2:
- Allocate cdev dynamically instead of having a fixed-size array

Hello,

I'm planning to queue this patch to the mtd/fixes PR. Arnd, Kees, feel
free to add your R-b.

Regards,

Boris
---
 drivers/mtd/maps/sa1100-flash.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/maps/sa1100-flash.c b/drivers/mtd/maps/sa1100-flash.c
index 784c6e1a0391..fd5fe12d7461 100644
--- a/drivers/mtd/maps/sa1100-flash.c
+++ b/drivers/mtd/maps/sa1100-flash.c
@@ -221,7 +221,14 @@ static struct sa_info *sa1100_setup_mtd(struct platform_device *pdev,
 		info->mtd = info->subdev[0].mtd;
 		ret = 0;
 	} else if (info->num_subdev > 1) {
-		struct mtd_info *cdev[nr];
+		struct mtd_info **cdev;
+
+		cdev = kmalloc_array(nr, sizeof(*cdev), GFP_KERNEL);
+		if (!cdev) {
+			ret = -ENOMEM;
+			goto err;
+		}
+
 		/*
 		 * We detected multiple devices.  Concatenate them together.
 		 */
@@ -230,6 +237,7 @@ static struct sa_info *sa1100_setup_mtd(struct platform_device *pdev,
 
 		info->mtd = mtd_concat_create(cdev, info->num_subdev,
 					      plat->name);
+		kfree(cdev);
 		if (info->mtd == NULL) {
 			ret = -ENXIO;
 			goto err;
-- 
2.17.1