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Date: Mon, 15 Dec 2014 14:26:48 +0000 From: Luis Henriques <luis.henriques@...onical.com> To: linux-kernel@...r.kernel.org, stable@...r.kernel.org, kernel-team@...ts.ubuntu.com Cc: Marcelo Ricardo Leitner <mleitner@...hat.com>, "David S. Miller" <davem@...emloft.net>, Luis Henriques <luis.henriques@...onical.com> Subject: [PATCH 3.16.y-ckt 154/168] Fix race condition between vxlan_sock_add and vxlan_sock_release 3.16.7-ckt3 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Marcelo Leitner <mleitner@...hat.com> commit 00c83b01d58068dfeb2e1351cca6fccf2a83fa8f upstream. Currently, when trying to reuse a socket, vxlan_sock_add will grab vn->sock_lock, locate a reusable socket, inc refcount and release vn->sock_lock. But vxlan_sock_release() will first decrement refcount, and then grab that lock. refcnt operations are atomic but as currently we have deferred works which hold vs->refcnt each, this might happen, leading to a use after free (specially after vxlan_igmp_leave): CPU 1 CPU 2 deferred work vxlan_sock_add ... ... spin_lock(&vn->sock_lock) vs = vxlan_find_sock(); vxlan_sock_release dec vs->refcnt, reaches 0 spin_lock(&vn->sock_lock) vxlan_sock_hold(vs), refcnt=1 spin_unlock(&vn->sock_lock) hlist_del_rcu(&vs->hlist); vxlan_notify_del_rx_port(vs) spin_unlock(&vn->sock_lock) So when we look for a reusable socket, we check if it wasn't freed already before reusing it. Signed-off-by: Marcelo Ricardo Leitner <mleitner@...hat.com> Fixes: 7c47cedf43a8b3 ("vxlan: move IGMP join/leave to work queue") Signed-off-by: David S. Miller <davem@...emloft.net> Signed-off-by: Luis Henriques <luis.henriques@...onical.com> --- drivers/net/vxlan.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c index 032c52e1208a..24c1bef7abc6 100644 --- a/drivers/net/vxlan.c +++ b/drivers/net/vxlan.c @@ -2064,9 +2064,8 @@ static int vxlan_init(struct net_device *dev) spin_lock(&vn->sock_lock); vs = vxlan_find_sock(vxlan->net, ipv6 ? AF_INET6 : AF_INET, vxlan->dst_port); - if (vs) { + if (vs && atomic_add_unless(&vs->refcnt, 1, 0)) { /* If we have a socket with same port already, reuse it */ - atomic_inc(&vs->refcnt); vxlan_vs_add_dev(vs, vxlan); } else { /* otherwise make new socket outside of RTNL */ @@ -2545,12 +2544,9 @@ struct vxlan_sock *vxlan_sock_add(struct net *net, __be16 port, spin_lock(&vn->sock_lock); vs = vxlan_find_sock(net, ipv6 ? AF_INET6 : AF_INET, port); - if (vs) { - if (vs->rcv == rcv) - atomic_inc(&vs->refcnt); - else + if (vs && ((vs->rcv != rcv) || + !atomic_add_unless(&vs->refcnt, 1, 0))) vs = ERR_PTR(-EBUSY); - } spin_unlock(&vn->sock_lock); if (!vs) -- 2.1.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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