[PATCH] net: af_packet: Validate parameter size for PACKET_HDRLEN control message

[Guenter Roeck <linux@roeck-us.net>]

Building af_packet may fail with

In function ‘copy_from_user’,
    inlined from ‘packet_getsockopt’ at
    net/packet/af_packet.c:3215:21:
arch/x86/include/asm/uaccess_32.h:211:26: error: call to
    ‘copy_from_user_overflow’ declared with attribute error: copy_from_user()
    buffer size is not provably correct

if built with W=1 due to a missing parameter size validation.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 net/packet/af_packet.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index c7bfeff..1976b23 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3210,6 +3210,8 @@ static int packet_getsockopt(struct socket *sock, int level, int optname,
 		val = po->tp_version;
 		break;
 	case PACKET_HDRLEN:
+		if (len < sizeof(int))
+			return -EINVAL;
 		if (len > sizeof(int))
 			len = sizeof(int);
 		if (copy_from_user(&val, optval, len))
-- 
1.7.9.7