[PATCH net] net: ethtool: Fix RSS setting

[Saeed Mahameed <saeed@kernel.org>]

From: Saeed Mahameed <saeedm@nvidia.com>

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.

Fixes: 13e59344fb9d ("net: ethtool: add support for symmetric-xor RSS hash")
CC: Ahmed Zaki <ahmed.zaki@intel.com>
CC: David Wei <dw@davidwei.uk>,
CC: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
---
 net/ethtool/ioctl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index e645d751a5e8..223dcd25d88a 100644
--- a/net/ethtool/ioctl.c
+++ b/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;
 
-- 
2.45.2