On 2/22/23 14:59, Dan Carpenter wrote:
Here the code is testing to see if skb->len meets a minimum size
requirement. However if skb->len is very small then the ETH_HLEN
subtraction will result in a negative which is then type promoted
to an unsigned int and the condition will be true.
Generally, when you have an untrusted variable like skb->len, you
should move all the math to the other side of the comparison.
Fixes: 15865124feed ("staging: r8188eu: introduce new core dir for RTL8188eu driver")
Signed-off-by: Dan Carpenter <error27@xxxxxxxxx>
---
Compile tested only. This is basic algebra of moving parts of the
equation from one side to the other and I am surprisingly bad at
something that I was supposed to have learned in 9th grade.
drivers/staging/r8188eu/core/rtw_br_ext.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/staging/r8188eu/core/rtw_br_ext.c b/drivers/staging/r8188eu/core/rtw_br_ext.c
index a7c67014dde0..f49e32c33372 100644
--- a/drivers/staging/r8188eu/core/rtw_br_ext.c
+++ b/drivers/staging/r8188eu/core/rtw_br_ext.c
@@ -538,7 +538,7 @@ int nat25_db_handle(struct adapter *priv, struct sk_buff *skb, int method)
/*------------------------------------------------*/
struct ipv6hdr *iph = (struct ipv6hdr *)(skb->data + ETH_HLEN);
- if (sizeof(*iph) >= (skb->len - ETH_HLEN))
+ if (skb->len <= sizeof(*iph) + ETH_HLEN)
return -1;
switch (method) {
Tested-by: Philipp Hortmann <philipp.g.hortmann@xxxxxxxxx> # Edimax N150
