Staging: comedi: integer overflow in do_insnlist_ioctl()

There is an integer overflow here that could cause memory corruption
on 32 bit systems.

insnlist.n_insns could be a very high value size calculation for
kmalloc() could overflow resulting in a smaller "insns" than
expected.  In the for (i = 0; i < insnlist.n_insns; i++) {... loop
we would read past the end of the buffer, possibly corrupting memory
as well.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index ebdcecda3583..ed4853f194c4 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -670,6 +670,11 @@ static int do_insnlist_ioctl(struct comedi_device *dev,
                 goto error;
         }
 
+        if (sizeof(struct comedi_insn) * insnlist.n_insns < insnlist.n_insns) {
+                ret = -EINVAL;
+                goto error;
+        }
+
         insns =
             kmalloc(sizeof(struct comedi_insn) * insnlist.n_insns, GFP_KERNEL);
         if (!insns) {