Commit 10f42426 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

inet: implement lockless IP_TTL 



ip_select_ttl() is racy, because it reads inet->uc_ttl
without proper locking.

Add READ_ONCE()/WRITE_ONCE() annotations while
allowing IP_TTL socket option to be set/read without
holding the socket lock.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 08e39c0d

net/ipv4/ip_output.c

+1 −1
Original line number Diff line number Diff line
@@ -133,7 +133,7 @@ EXPORT_SYMBOL_GPL(ip_local_out); 
static inline int ip_select_ttl(const struct inet_sock *inet,

				const struct dst_entry *dst)

{

	int ttl = inet->uc_ttl;

	int ttl = READ_ONCE(inet->uc_ttl);



	if (ttl < 0)

		ttl = ip4_dst_hoplimit(dst);

net/ipv4/ip_sockglue.c

+12 −15
Original line number Diff line number Diff line
@@ -1023,6 +1023,13 @@ int do_ip_setsockopt(struct sock *sk, int level, int optname, 
	case IP_BIND_ADDRESS_NO_PORT:

		inet_assign_bit(BIND_ADDRESS_NO_PORT, sk, val);

		return 0;

	case IP_TTL:

		if (optlen < 1)

			return -EINVAL;

		if (val != -1 && (val < 1 || val > 255))

			return -EINVAL;

		WRITE_ONCE(inet->uc_ttl, val);

		return 0;

	}



	err = 0;
@@ -1080,13 +1087,6 @@ int do_ip_setsockopt(struct sock *sk, int level, int optname, 
	case IP_TOS:	/* This sets both TOS and Precedence */

		__ip_sock_set_tos(sk, val);

		break;

	case IP_TTL:

		if (optlen < 1)

			goto e_inval;

		if (val != -1 && (val < 1 || val > 255))

			goto e_inval;

		inet->uc_ttl = val;

		break;

	case IP_MTU_DISCOVER:

		if (val < IP_PMTUDISC_DONT || val > IP_PMTUDISC_OMIT)

			goto e_inval;
@@ -1590,6 +1590,11 @@ int do_ip_getsockopt(struct sock *sk, int level, int optname, 
	case IP_BIND_ADDRESS_NO_PORT:

		val = inet_test_bit(BIND_ADDRESS_NO_PORT, sk);

		goto copyval;

	case IP_TTL:

		val = READ_ONCE(inet->uc_ttl);

		if (val < 0)

			val = READ_ONCE(sock_net(sk)->ipv4.sysctl_ip_default_ttl);

		goto copyval;

	}



	if (needs_rtnl)
@@ -1629,14 +1634,6 @@ int do_ip_getsockopt(struct sock *sk, int level, int optname, 
	case IP_TOS:

		val = inet->tos;

		break;

	case IP_TTL:

	{

		struct net *net = sock_net(sk);

		val = (inet->uc_ttl == -1 ?

		       READ_ONCE(net->ipv4.sysctl_ip_default_ttl) :

		       inet->uc_ttl);

		break;

	}

	case IP_MTU_DISCOVER:

		val = inet->pmtudisc;

		break;