linux-kernel - [PATCH v2] comedi: integer overflow in do_insnlist

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Message-Id: <6414679A-65C7-46EA-A4D7-3CFC02780D28@gmail.com>
Date:	Wed, 23 Nov 2011 11:53:01 -0500
From:	Xi Wang <xi.wang@...il.com>
To:	Ian Abbott <abbotti@....co.uk>
Cc:	Dan Carpenter <dan.carpenter@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	Mori Hess <fmhess@...rs.sourceforge.net>,
	"security@...nel.org" <security@...nel.org>,
	Lucas De Marchi <lucas.demarchi@...fusion.mobi>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Ian Abbott <ian.abbott@....co.uk>,
	Franky Lin <frankyl@...adcom.com>,
	Greg Dietsche <Gregory.Dietsche@....edu>,
	Mark Pearson <markpearson_de@...oo.de>
Subject: [PATCH v2] comedi: integer overflow in do_insnlist_ioctl()

There is a potential integer overflow in do_insnlist_ioctl() if
userspace passes in a large insnlist.n_insns. The call to kmalloc()
would allocate a small buffer, leading to a memory corruption.

Reported-by: Haogang Chen <haogangchen@...il.com>
Suggested-by: Dan Carpenter <dan.carpenter@...cle.com>
Suggested-by: Ian Abbott <abbotti@....co.uk>
Signed-off-by: Xi Wang <xi.wang@...il.com>
---
 drivers/staging/comedi/comedi_fops.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index 21d8c1c..df86a9e 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -670,8 +670,9 @@ static int do_insnlist_ioctl(struct comedi_device *dev,
 		goto error;
 	}
 
-	insns =
-	    kmalloc(sizeof(struct comedi_insn) * insnlist.n_insns, GFP_KERNEL);
+	if (insnlist.n_insns <= ULONG_MAX / sizeof(struct comedi_insn))
+		insns = kmalloc(sizeof(struct comedi_insn) * insnlist.n_insns,
+				GFP_KERNEL);
 	if (!insns) {
 		DPRINTK("kmalloc failed\n");
 		ret = -ENOMEM;
-- 
1.7.5.4


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