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

[Xi Wang]

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@xxxxxxxxxx>
and Haogang Chen <haogangchen@xxxxxxxxx>.  The patch was suggested by
Ian Abbott <abbotti@xxxxxxxxx> and Lars-Peter Clausen <lars@xxxxxxxxxx>.

Signed-off-by: Xi Wang <xi.wang@xxxxxxxxx>
---
 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

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