ethtool: Fix potential user buffer overflow for ETHTOOL_{G, S}RXFH

struct ethtool_rxnfc was originally defined in 2.6.27 for the
ETHTOOL_{G,S}RXFH command with only the cmd, flow_type and data
fields.  It was then extended in 2.6.30 to support various additional
commands.  These commands should have been defined to use a new
structure, but it is too late to change that now.

Since user-space may still be using the old structure definition
for the ETHTOOL_{G,S}RXFH commands, and since they do not need the
additional fields, only copy the originally defined fields to and
from user-space.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 276b40a..b4207ca 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -379,6 +379,8 @@ struct ethtool_rxnfc {
 	__u32				flow_type;
 	/* The rx flow hash value or the rule DB size */
 	__u64				data;
+	/* The following fields are not valid and must not be used for
+	 * the ETHTOOL_{G,X}RXFH commands. */
 	struct ethtool_rx_flow_spec	fs;
 	__u32				rule_cnt;
 	__u32				rule_locs[0];