From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mms2.broadcom.com ([216.31.210.18]) by canuck.infradead.org with esmtp (Exim 4.72 #1 (Red Hat Linux)) id 1PGQmh-0004om-Kl for linux-mtd@lists.infradead.org; Thu, 11 Nov 2010 06:37:24 +0000 From: "Brian Norris" To: linux-mtd@lists.infradead.org Subject: [PATCH v2 08/10] mtd-utils: nandwrite: prevent 32-bit overflow Date: Wed, 10 Nov 2010 22:31:41 -0800 Message-ID: <1289457101-24040-1-git-send-email-computersforpeace@gmail.com> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Brian Norris , David Woodhouse , Mike Frysinger , Artem Bityutskiy List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , For large block- and page-sizes, the multiplication of ebsize_aligned and pagelen can overflow a 32-bit integer. This overflow can be prevented by a simple change in order of operations (i.e., do division first). Since ebsize_aligned is always a multiple of mtd.min_io_size, this produces no change in results. Signed-off-by: Brian Norris --- nandwrite.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-) diff --git a/nandwrite.c b/nandwrite.c index 8ec5afe..aea7572 100644 --- a/nandwrite.c +++ b/nandwrite.c @@ -440,8 +440,13 @@ int main(int argc, char * const argv[]) goto closeall; } - // Allocate a buffer big enough to contain all the data (OOB included) for one eraseblock - filebuf_max = pagelen * ebsize_aligned / mtd.min_io_size; + /* + * Allocate a buffer big enough to contain all the data (OOB included) + * for one eraseblock. The order of operations here matters; if ebsize + * and pagelen are large enough, then "ebsize_aligned * pagelen" could + * overflow a 32-bit data type. + */ + filebuf_max = ebsize_aligned / mtd.min_io_size * pagelen; filebuf = xmalloc(filebuf_max); erase_buffer(filebuf, filebuf_max); -- 1.7.0.4