Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.2 17/30] netlink: Fix autobind race condition that leads to zero port ID | Date | Thu, 1 Oct 2015 11:21:39 +0200 |
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4.2-stable review patch. If anyone has any objections, please let me know.
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From: Herbert Xu <herbert@gondor.apana.org.au>
[ 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@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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- 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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