linux-kernel - [PATCH] nvmem: rave-sp-eeprom: Remove VLA usage

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Message-ID: <20180620182600.GA24297@beast>
Date:   Wed, 20 Jun 2018 11:26:00 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Andrey Smirnov <andrew.smirnov@...il.com>
Subject: [PATCH] nvmem: rave-sp-eeprom: Remove VLA usage

In the quest to remove all stack VLA usage from the kernel[1], this
uses the maximum allocation size for the stack and adds a sanity check,
similar to what has already be done for the regular rave-sp driver.

[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/nvmem/rave-sp-eeprom.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/nvmem/rave-sp-eeprom.c b/drivers/nvmem/rave-sp-eeprom.c
index 50aeea6ec6cc..66699d44f73d 100644
--- a/drivers/nvmem/rave-sp-eeprom.c
+++ b/drivers/nvmem/rave-sp-eeprom.c
@@ -35,6 +35,7 @@ enum rave_sp_eeprom_header_size {
 	RAVE_SP_EEPROM_HEADER_SMALL = 4U,
 	RAVE_SP_EEPROM_HEADER_BIG   = 5U,
 };
+#define RAVE_SP_EEPROM_HEADER_MAX	RAVE_SP_EEPROM_HEADER_BIG
 
 #define	RAVE_SP_EEPROM_PAGE_SIZE	32U
 
@@ -97,9 +98,12 @@ static int rave_sp_eeprom_io(struct rave_sp_eeprom *eeprom,
 	const unsigned int rsp_size =
 		is_write ? sizeof(*page) - sizeof(page->data) : sizeof(*page);
 	unsigned int offset = 0;
-	u8 cmd[cmd_size];
+	u8 cmd[RAVE_SP_EEPROM_HEADER_MAX + sizeof(page->data)];
 	int ret;
 
+	if (WARN_ON(cmd_size > sizeof(cmd)))
+		return -EINVAL;
+
 	cmd[offset++] = eeprom->address;
 	cmd[offset++] = 0;
 	cmd[offset++] = type;
-- 
2.17.1


-- 
Kees Cook
Pixel Security