4.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
[ Upstream commit 1f770c0a09da855a2b51af6d19de97fb955eca85 ]
The commit c0bb07df7d981e4091432754e30c9c720e2c0c78 ("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: c0bb07df7d98 ("netlink: Reset portid after netlink_insert failure")
Reported-by: Tejun Heo <tj@xxxxxxxxxx>
Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/netlink/af_netlink.c | 12 +++++++-----
net/netlink/af_netlink.h | 1 +
2 files changed, 8 insertions(+), 5 deletions(-)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -1019,7 +1019,7 @@ static inline int netlink_compare(struct
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));
}
@@ -1045,7 +1045,7 @@ static int __netlink_insert(struct netli
{
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);
@@ -1107,7 +1107,7 @@ static int netlink_insert(struct sock *s
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);
@@ -1119,10 +1119,12 @@ static int netlink_insert(struct sock *s
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;
@@ -3233,7 +3235,7 @@ static inline u32 netlink_hash(const voi
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);
}
--- a/net/netlink/af_netlink.h
+++ b/net/netlink/af_netlink.h
@@ -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;
--
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