[PATCH AUTOSEL 5.6 215/606] net: inet_csk: Fix so_reuseport bind-address cache in tb->fast*

Sasha Levin
2020-06-09T00:28:00Z

From: Martin KaFai Lau <kafai@fb.com>

[ Upstream commit 88d7fcfa3b1fe670f0412b95be785aafca63352b ]

The commit 637bc8bbe6c0 ("inet: reset tb->fastreuseport when adding a reuseport sk")
added a bind-address cache in tb->fast*. The tb->fast* caches the address
of a sk which has successfully been binded with SO_REUSEPORT ON. The idea
is to avoid the expensive conflict search in inet_csk_bind_conflict().

There is an issue with wildcard matching where sk_reuseport_match() should
have returned false but it is currently returning true. It ends up
hiding bind conflict. For example,

bind("[::1]:443"); /* without SO_REUSEPORT. Succeed. */
bind("[::2]:443"); /* with SO_REUSEPORT. Succeed. */
bind("[::]:443"); /* with SO_REUSEPORT. Still Succeed where it shouldn't */

The last bind("[::]:443") with SO_REUSEPORT on should have failed because
it should have a conflict with the very first bind("[::1]:443") which
has SO_REUSEPORT off. However, the address "[::2]" is cached in
tb->fast* in the second bind. In the last bind, the sk_reuseport_match()
returns true because the binding sk's wildcard addr "[::]" matches with
the "[::2]" cached in tb->fast*.

The correct bind conflict is reported by removing the second
bind such that tb->fast* cache is not involved and forces the
bind("[::]:443") to go through the inet_csk_bind_conflict():

bind("[::1]:443"); /* without SO_REUSEPORT. Succeed. */
bind("[::]:443"); /* with SO_REUSEPORT. -EADDRINUSE */

The expected behavior for sk_reuseport_match() is, it should only allow
the "cached" tb->fast* address to be used as a wildcard match but not
the address of the binding sk. To do that, the current
"bool match_wildcard" arg is split into
"bool match_sk1_wildcard" and "bool match_sk2_wildcard".

This change only affects the sk_reuseport_match() which is only
used by inet_csk (e.g. TCP).
The other use cases are calling inet_rcv_saddr_equal() and
this patch makes it pass the same "match_wildcard" arg twice to
the "ipv[46]_rcv_saddr_equal(..., match_wildcard, match_wildcard)".

Cc: Josef Bacik <jbacik@fb.com>
Fixes: 637bc8bbe6c0 ("inet: reset tb->fastreuseport when adding a reuseport sk")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv4/inet_connection_sock.c | 43 ++++++++++++++++++---------------
1 file changed, 24 insertions(+), 19 deletions(-)

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index d545fb99a8a1..76afe93904d5 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -24,17 +24,19 @@
#include <net/addrconf.h>

#if IS_ENABLED(CONFIG_IPV6)
-/* match_wildcard == true: IPV6_ADDR_ANY equals to any IPv6 addresses if IPv6
- * only, and any IPv4 addresses if not IPv6 only
- * match_wildcard == false: addresses must be exactly the same, i.e.
- * IPV6_ADDR_ANY only equals to IPV6_ADDR_ANY,
- * and 0.0.0.0 equals to 0.0.0.0 only
+/* match_sk*_wildcard == true: IPV6_ADDR_ANY equals to any IPv6 addresses
+ * if IPv6 only, and any IPv4 addresses
+ * if not IPv6 only
+ * match_sk*_wildcard == false: addresses must be exactly the same, i.e.
+ * IPV6_ADDR_ANY only equals to IPV6_ADDR_ANY,
+ * and 0.0.0.0 equals to 0.0.0.0 only
*/
static bool ipv6_rcv_saddr_equal(const struct in6_addr *sk1_rcv_saddr6,
const struct in6_addr *sk2_rcv_saddr6,
__be32 sk1_rcv_saddr, __be32 sk2_rcv_saddr,
bool sk1_ipv6only, bool sk2_ipv6only,
- bool match_wildcard)
+ bool match_sk1_wildcard,
+ bool match_sk2_wildcard)
{
int addr_type = ipv6_addr_type(sk1_rcv_saddr6);
int addr_type2 = sk2_rcv_saddr6 ? ipv6_addr_type(sk2_rcv_saddr6) : IPV6_ADDR_MAPPED;
@@ -44,8 +46,8 @@ static bool ipv6_rcv_saddr_equal(const struct in6_addr *sk1_rcv_saddr6,
if (!sk2_ipv6only) {
if (sk1_rcv_saddr == sk2_rcv_saddr)
return true;
- if (!sk1_rcv_saddr || !sk2_rcv_saddr)
- return match_wildcard;
+ return (match_sk1_wildcard && !sk1_rcv_saddr) ||
+ (match_sk2_wildcard && !sk2_rcv_saddr);
}
return false;
}
@@ -53,11 +55,11 @@ static bool ipv6_rcv_saddr_equal(const struct in6_addr *sk1_rcv_saddr6,
if (addr_type == IPV6_ADDR_ANY && addr_type2 == IPV6_ADDR_ANY)
return true;

- if (addr_type2 == IPV6_ADDR_ANY && match_wildcard &&
+ if (addr_type2 == IPV6_ADDR_ANY && match_sk2_wildcard &&
!(sk2_ipv6only && addr_type == IPV6_ADDR_MAPPED))
return true;

- if (addr_type == IPV6_ADDR_ANY && match_wildcard &&
+ if (addr_type == IPV6_ADDR_ANY && match_sk1_wildcard &&
!(sk1_ipv6only && addr_type2 == IPV6_ADDR_MAPPED))
return true;

@@ -69,18 +71,19 @@ static bool ipv6_rcv_saddr_equal(const struct in6_addr *sk1_rcv_saddr6,
}
#endif

-/* match_wildcard == true: 0.0.0.0 equals to any IPv4 addresses
- * match_wildcard == false: addresses must be exactly the same, i.e.
- * 0.0.0.0 only equals to 0.0.0.0
+/* match_sk*_wildcard == true: 0.0.0.0 equals to any IPv4 addresses
+ * match_sk*_wildcard == false: addresses must be exactly the same, i.e.
+ * 0.0.0.0 only equals to 0.0.0.0
*/
static bool ipv4_rcv_saddr_equal(__be32 sk1_rcv_saddr, __be32 sk2_rcv_saddr,
- bool sk2_ipv6only, bool match_wildcard)
+ bool sk2_ipv6only, bool match_sk1_wildcard,
+ bool match_sk2_wildcard)
{
if (!sk2_ipv6only) {
if (sk1_rcv_saddr == sk2_rcv_saddr)
return true;
- if (!sk1_rcv_saddr || !sk2_rcv_saddr)
- return match_wildcard;
+ return (match_sk1_wildcard && !sk1_rcv_saddr) ||
+ (match_sk2_wildcard && !sk2_rcv_saddr);
}
return false;
}
@@ -96,10 +99,12 @@ bool inet_rcv_saddr_equal(const struct sock *sk, const struct sock *sk2,
sk2->sk_rcv_saddr,
ipv6_only_sock(sk),
ipv6_only_sock(sk2),
+ match_wildcard,
match_wildcard);
#endif
return ipv4_rcv_saddr_equal(sk->sk_rcv_saddr, sk2->sk_rcv_saddr,
- ipv6_only_sock(sk2), match_wildcard);
+ ipv6_only_sock(sk2), match_wildcard,
+ match_wildcard);
}
EXPORT_SYMBOL(inet_rcv_saddr_equal);

@@ -273,10 +278,10 @@ static inline int sk_reuseport_match(struct inet_bind_bucket *tb,
tb->fast_rcv_saddr,
sk->sk_rcv_saddr,
tb->fast_ipv6_only,
- ipv6_only_sock(sk), true);
+ ipv6_only_sock(sk), true, false);
#endif
return ipv4_rcv_saddr_equal(tb->fast_rcv_saddr, sk->sk_rcv_saddr,
- ipv6_only_sock(sk), true);
+ ipv6_only_sock(sk), true, false);
}

/* Obtain a reference to a local port for the given sock,
--
2.25.1