Commit fa17a6d8 authored by Eric Dumazet's avatar Eric Dumazet Committed by Paolo Abeni
Browse files

ipv6: lockless IPV6_ADDR_PREFERENCES implementation 



We have data-races while reading np->srcprefs

Switch the field to a plain byte, add READ_ONCE()
and WRITE_ONCE() annotations where needed,
and IPV6_ADDR_PREFERENCES setsockopt() can now be lockless.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarDavid Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20230918142321.1794107-1-edumazet@google.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent 6a23c555

include/linux/ipv6.h

+1 −1
Original line number Diff line number Diff line
@@ -243,7 +243,7 @@ struct ipv6_pinfo { 
	} rxopt;



	/* sockopt flags */

	__u8			srcprefs:3;	/* 001: prefer temporary address

	__u8			srcprefs;	/* 001: prefer temporary address

						 * 010: prefer public address

						 * 100: prefer care-of address

						 */

include/net/ip6_route.h

+2 −3
Original line number Diff line number Diff line
@@ -53,13 +53,12 @@ struct route_info { 
 */

static inline int rt6_srcprefs2flags(unsigned int srcprefs)

{

	/* No need to bitmask because srcprefs have only 3 bits. */

	return srcprefs << 3;

	return (srcprefs & IPV6_PREFER_SRC_MASK) << 3;

}



static inline unsigned int rt6_flags2srcprefs(int flags)

{

	return (flags >> 3) & 7;

	return (flags >> 3) & IPV6_PREFER_SRC_MASK;

}



static inline bool rt6_need_strict(const struct in6_addr *daddr)

include/net/ipv6.h

+7 −13
Original line number Diff line number Diff line
@@ -1306,10 +1306,13 @@ static inline void ip6_sock_set_recverr(struct sock *sk) 
	inet6_set_bit(RECVERR6, sk);

}



static inline int __ip6_sock_set_addr_preferences(struct sock *sk, int val)

#define IPV6_PREFER_SRC_MASK (IPV6_PREFER_SRC_TMP | IPV6_PREFER_SRC_PUBLIC | \

			      IPV6_PREFER_SRC_COA)



static inline int ip6_sock_set_addr_preferences(struct sock *sk, int val)

{

	unsigned int prefmask = ~IPV6_PREFER_SRC_MASK;

	unsigned int pref = 0;

	unsigned int prefmask = ~0;



	/* check PUBLIC/TMP/PUBTMP_DEFAULT conflicts */

	switch (val & (IPV6_PREFER_SRC_PUBLIC |
@@ -1359,20 +1362,11 @@ static inline int __ip6_sock_set_addr_preferences(struct sock *sk, int val) 
		return -EINVAL;

	}



	inet6_sk(sk)->srcprefs = (inet6_sk(sk)->srcprefs & prefmask) | pref;

	WRITE_ONCE(inet6_sk(sk)->srcprefs,

		   (READ_ONCE(inet6_sk(sk)->srcprefs) & prefmask) | pref);

	return 0;

}



static inline int ip6_sock_set_addr_preferences(struct sock *sk, int val)

{

	int ret;



	lock_sock(sk);

	ret = __ip6_sock_set_addr_preferences(sk, val);

	release_sock(sk);

	return ret;

}



static inline void ip6_sock_set_recvpktinfo(struct sock *sk)

{

	lock_sock(sk);

net/ipv6/ip6_output.c

+1 −1
Original line number Diff line number Diff line
@@ -1113,7 +1113,7 @@ static int ip6_dst_lookup_tail(struct net *net, const struct sock *sk, 
		rcu_read_lock();

		from = rt ? rcu_dereference(rt->from) : NULL;

		err = ip6_route_get_saddr(net, from, &fl6->daddr,

					  sk ? inet6_sk(sk)->srcprefs : 0,

					  sk ? READ_ONCE(inet6_sk(sk)->srcprefs) : 0,

					  &fl6->saddr);

		rcu_read_unlock();

net/ipv6/ipv6_sockglue.c

+10 −9
Original line number Diff line number Diff line
@@ -505,6 +505,10 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname, 
			return -EINVAL;

		inet6_assign_bit(SNDFLOW, sk, valbool);

		return 0;

	case IPV6_ADDR_PREFERENCES:

		if (optlen < sizeof(int))

			return -EINVAL;

		return ip6_sock_set_addr_preferences(sk, val);

	}

	if (needs_rtnl)

		rtnl_lock();
@@ -964,11 +968,6 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname, 
		retv = xfrm_user_policy(sk, optname, optval, optlen);

		break;



	case IPV6_ADDR_PREFERENCES:

		if (optlen < sizeof(int))

			goto e_inval;

		retv = __ip6_sock_set_addr_preferences(sk, val);

		break;

	case IPV6_RECVFRAGSIZE:

		np->rxopt.bits.recvfragsize = valbool;

		retv = 0;
@@ -1415,23 +1414,25 @@ int do_ipv6_getsockopt(struct sock *sk, int level, int optname, 
	}



	case IPV6_ADDR_PREFERENCES:

		{

		u8 srcprefs = READ_ONCE(np->srcprefs);

		val = 0;



		if (np->srcprefs & IPV6_PREFER_SRC_TMP)

		if (srcprefs & IPV6_PREFER_SRC_TMP)

			val |= IPV6_PREFER_SRC_TMP;

		else if (np->srcprefs & IPV6_PREFER_SRC_PUBLIC)

		else if (srcprefs & IPV6_PREFER_SRC_PUBLIC)

			val |= IPV6_PREFER_SRC_PUBLIC;

		else {

			/* XXX: should we return system default? */

			val |= IPV6_PREFER_SRC_PUBTMP_DEFAULT;

		}



		if (np->srcprefs & IPV6_PREFER_SRC_COA)

		if (srcprefs & IPV6_PREFER_SRC_COA)

			val |= IPV6_PREFER_SRC_COA;

		else

			val |= IPV6_PREFER_SRC_HOME;

		break;



		}

	case IPV6_MINHOPCOUNT:

		val = READ_ONCE(np->min_hopcount);

		break;