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netlink: Fix autobind race condition that leads to zero port ID 

The commit c0bb07df7d ("netlink:
Reset portid after netlink_insert failure") introduced a race
condition where if two threads try to autobind the same socket
one of them may end up with a zero port ID.  This led to kernel
deadlocks that were observed by multiple people.

This patch reverts that commit and instead fixes it by introducing
a separte rhash_portid variable so that the real portid is only set
after the socket has been successfully hashed.

Fixes: c0bb07df7d ("netlink: Reset portid after netlink_insert failure")
Reported-by: Tejun Heo <tj@kernel.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2015-09-18 19:16:50 +08:00 committed by David S. Miller
parent 3ea79249e8
commit 1f770c0a09
2 changed files with 8 additions and 5 deletions
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12
net/netlink/af_netlink.c
View File

@ -1031,7 +1031,7 @@ static inline int netlink_compare(struct rhashtable_compare_arg *arg,
const struct netlink_compare_arg *x = arg->key;
const struct netlink_sock *nlk = ptr;
return nlk->portid != x->portid ||
return nlk->rhash_portid != x->portid ||
!net_eq(sock_net(&nlk->sk), read_pnet(&x->pnet));
}
@ -1057,7 +1057,7 @@ static int __netlink_insert(struct netlink_table *table, struct sock *sk)
{
struct netlink_compare_arg arg;
netlink_compare_arg_init(&arg, sock_net(sk), nlk_sk(sk)->portid);
netlink_compare_arg_init(&arg, sock_net(sk), nlk_sk(sk)->rhash_portid);
return rhashtable_lookup_insert_key(&table->hash, &arg,
&nlk_sk(sk)->node,
netlink_rhashtable_params);
@ -1119,7 +1119,7 @@ static int netlink_insert(struct sock *sk, u32 portid)
unlikely(atomic_read(&table->hash.nelems) >= UINT_MAX))
goto err;
nlk_sk(sk)->portid = portid;
nlk_sk(sk)->rhash_portid = portid;
sock_hold(sk);
err = __netlink_insert(table, sk);
@ -1131,10 +1131,12 @@ static int netlink_insert(struct sock *sk, u32 portid)
err = -EOVERFLOW;
if (err == -EEXIST)
err = -EADDRINUSE;
nlk_sk(sk)->portid = 0;
sock_put(sk);
goto err;
}
nlk_sk(sk)->portid = portid;
err:
release_sock(sk);
return err;
@ -3271,7 +3273,7 @@ static inline u32 netlink_hash(const void *data, u32 len, u32 seed)
const struct netlink_sock *nlk = data;
struct netlink_compare_arg arg;
netlink_compare_arg_init(&arg, sock_net(&nlk->sk), nlk->portid);
netlink_compare_arg_init(&arg, sock_net(&nlk->sk), nlk->rhash_portid);
return jhash2((u32 *)&arg, netlink_compare_arg_len / sizeof(u32), seed);
}

1
net/netlink/af_netlink.h
View File

@ -25,6 +25,7 @@ struct netlink_ring {
struct netlink_sock {
/* struct sock has to be the first member of netlink_sock */
struct sock sk;
u32 rhash_portid;
u32 portid;
u32 dst_portid;
u32 dst_group;