[PATCH v3] comedi: integer overflow in do_insnlist_ioctl()

[Xi Wang <xi.wang@gmail.com>]

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.

The bug was reported by Dan Carpenter <dan.carpenter@oracle.com>
and Haogang Chen <haogangchen@gmail.com>.  The patch was suggested by
Ian Abbott <abbotti@mev.co.uk> and Lars-Peter Clausen <lars@metafoo.de>.

Signed-off-by: Xi Wang <xi.wang@gmail.com>
---
  drivers/staging/comedi/comedi_fops.c |    2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/staging/comedi/comedi_fops.c 
b/drivers/staging/comedi/comedi_fops.c
index 21d8c1c..7f7d79e 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -671,7 +671,7 @@ static int do_insnlist_ioctl(struct comedi_device *dev,
  	}

  	insns =
-	    kmalloc(sizeof(struct comedi_insn) * insnlist.n_insns, GFP_KERNEL);
+	    kcalloc(insnlist.n_insns, sizeof(struct comedi_insn), GFP_KERNEL);
  	if (!insns) {
  		DPRINTK("kmalloc failed\n");
  		ret = -ENOMEM;
-- 
1.7.5.4