If "newmtu * 2 + 4" is too large then it can cause an integer overflow
leading to memory corruption. Eric Dumazet suggests that 65534 is a
reasonable upper limit.
Btw, "newmtu" is not allowed to be a negative number because of the
check in dev_set_mtu(), so that's ok.
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
---
v2: Cap it at 65534 instead of just testing for integer overflows.
Thanks David and Eric!
diff --git a/drivers/net/wan/x25_asy.c b/drivers/net/wan/x25_asy.c
index df6c073..5c47b01 100644
--- a/drivers/net/wan/x25_asy.c
+++ b/drivers/net/wan/x25_asy.c
@@ -122,8 +122,12 @@ static int x25_asy_change_mtu(struct net_device *dev, int newmtu)
{
struct x25_asy *sl = netdev_priv(dev);
unsigned char *xbuff, *rbuff;
- int len = 2 * newmtu;
+ int len;
+ if (newmtu > 65534)
+ return -EINVAL;
+
+ len = 2 * newmtu;
xbuff = kmalloc(len + 4, GFP_ATOMIC);
rbuff = kmalloc(len + 4, GFP_ATOMIC);
--
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