gcc-8 has a new warning that detects overlapping input and output arguments in memcpy(). It triggers for sit_init_net() calling ipip6_tunnel_clone_6rd(), which is actually correct:
net/ipv6/sit.c: In function 'sit_init_net': net/ipv6/sit.c:192:3: error: 'memcpy' source argument is the same as destination [-Werror=restrict]
The problem here is that the logic detecting the memcpy() arguments finds them to be the same, but the conditional that tests for the input and output of ipip6_tunnel_clone_6rd() to be identical is not a compile-time constant.
We know that netdev_priv(t->dev) is the same as t for a tunnel device, and comparing "dev" directly here lets the compiler figure out as well that 'dev == sitn->fb_tunnel_dev' when called from sit_init_net(), so it no longer warns.
This code is old, so Cc stable to make sure that we don't get the warning for older kernels built with new gcc.
Cc: stable@vger.kernel.org Cc: Martin Sebor msebor@gmail.com Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83456 Signed-off-by: Arnd Bergmann arnd@arndb.de --- net/ipv6/sit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c index 3873d3877135..3a1775a62973 100644 --- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -182,7 +182,7 @@ static void ipip6_tunnel_clone_6rd(struct net_device *dev, struct sit_net *sitn) #ifdef CONFIG_IPV6_SIT_6RD struct ip_tunnel *t = netdev_priv(dev);
- if (t->dev == sitn->fb_tunnel_dev) { + if (dev == sitn->fb_tunnel_dev) { ipv6_addr_set(&t->ip6rd.prefix, htonl(0x20020000), 0, 0, 0); t->ip6rd.relay_prefix = 0; t->ip6rd.prefixlen = 16;