Hi!
[ Upstream commit 513d9a61156d79dd0979c4ad400c8587f52cbb9d ]
CFI (Control Flow Integrity) is a safety feature allowing the system to detect and react should a potential control flow hijacking occurs. In particular, the Forward-Edge CFI protects indirect function calls by ensuring the prototype of function that is actually called matches the definition of the function hook.
Since Linux now supports CFI, it will be a good idea to fix mismatched return type for implementation of hooks. Otherwise this would get cought out by CFI and cause a panic.
Use enums from netdev_tx_t as return value instead, then change return type to netdev_tx_t. Note that rtllib_xmit_inter() would return 1 only on allocation failure and the queue is stopped if that happens, meeting the documented requirement if NETDEV_TX_BUSY should be returned by ndo_start_xmit.
+++ b/drivers/staging/rtl8192e/rtllib_tx.c @@ -964,9 +964,9 @@ static int rtllib_xmit_inter(struct sk_buff *skb, struct net_device *dev) } -int rtllib_xmit(struct sk_buff *skb, struct net_device *dev) +netdev_tx_t rtllib_xmit(struct sk_buff *skb, struct net_device *dev) { memset(skb->cb, 0, sizeof(skb->cb));
- return rtllib_xmit_inter(skb, dev);
- return rtllib_xmit_inter(skb, dev) ? NETDEV_TX_BUSY : NETDEV_TX_OK;
} EXPORT_SYMBOL(rtllib_xmit);
First, rtllib_xmit_inter() should be fixed to return the enum, too.
Second, we really should not take this to stable, as CFI is not available there. We should drop these patches:
4.19 14/19] staging: rtl8192u: Fix return type of ieee80211_xmit 5.10 09/33] staging: rtl8712: Fix return type for implementation of ndo_start_xmit 5.10 10/33] staging: rtl8192e: Fix return type for implementation of ndo_start_xmit
Thank you, Pavel