net: ethtool: Fix RSS setting

When user submits a rxfh set command without touching XFRM_SYM_XOR,
rxfh.input_xfrm is set to RXH_XFRM_NO_CHANGE, which is equal to 0xff.

Testing if (rxfh.input_xfrm & RXH_XFRM_SYM_XOR &&
	    !ops->cap_rss_sym_xor_supported)
		return -EOPNOTSUPP;

Will always be true on devices that don't set cap_rss_sym_xor_supported,
since rxfh.input_xfrm & RXH_XFRM_SYM_XOR is always true, if input_xfrm
was not set, i.e RXH_XFRM_NO_CHANGE=0xff, which will result in failure
of any command that doesn't require any change of XFRM, e.g RSS context
or hash function changes.

To avoid this breakage, test if rxfh.input_xfrm != RXH_XFRM_NO_CHANGE
before testing other conditions. Note that the problem will only trigger
with XFRM-aware userspace, old ethtool CLI would continue to work.

Fixes: 0dd415d ("net: ethtool: add a NO_CHANGE uAPI for new RXFH's input_xfrm")
Signed-off-by: Saeed Mahameed <[email protected]>
Reviewed-by: Ahmed Zaki <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Saeed Mahameed

net/ethtool/ioctl.c

@@ -1306,7 +1306,8 @@ static noinline_for_stack int ethtool_set_rxfh(struct net_device *dev,
 	if (rxfh.input_xfrm && rxfh.input_xfrm != RXH_XFRM_SYM_XOR &&
 	    rxfh.input_xfrm != RXH_XFRM_NO_CHANGE)
 		return -EINVAL;
-	if ((rxfh.input_xfrm & RXH_XFRM_SYM_XOR) &&
+	if (rxfh.input_xfrm != RXH_XFRM_NO_CHANGE &&
+	    (rxfh.input_xfrm & RXH_XFRM_SYM_XOR) &&
 	    !ops->cap_rss_sym_xor_supported)
 		return -EOPNOTSUPP;