From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Greg Thelen , Eric Dumazet , "David S. Miller" Subject: [PATCH 4.1 20/95] net: fix a race in dst_release() Date: Mon, 7 Dec 2015 09:35:14 -0500 Message-Id: <20151207142740.335655047@linuxfoundation.org> In-Reply-To: <20151207142739.317088107@linuxfoundation.org> References: <20151207142739.317088107@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit d69bbf88c8d0b367cf3e3a052f6daadf630ee566 ] Only cpu seeing dst refcount going to 0 can safely dereference dst->flags. Otherwise an other cpu might already have freed the dst. Fixes: 27b75c95f10d ("net: avoid RCU for NOCACHE dst") Reported-by: Greg Thelen Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/core/dst.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/core/dst.c +++ b/net/core/dst.c @@ -285,7 +285,7 @@ void dst_release(struct dst_entry *dst) newrefcnt = atomic_dec_return(&dst->__refcnt); WARN_ON(newrefcnt < 0); - if (unlikely(dst->flags & DST_NOCACHE) && !newrefcnt) + if (!newrefcnt && unlikely(dst->flags & DST_NOCACHE)) call_rcu(&dst->rcu_head, dst_destroy_rcu); } }