From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Westphal Subject: [PATCH net-next 2/6] xfrm: state: use atomic_inc_not_zero to increment refcount Date: Tue, 9 Aug 2016 12:16:05 +0200 Message-ID: <1470737769-30438-3-git-send-email-fw@strlen.de> References: <1470737769-30438-1-git-send-email-fw@strlen.de> Cc: Florian Westphal To: Return-path: Received: from Chamillionaire.breakpoint.cc ([146.0.238.67]:43906 "EHLO Chamillionaire.breakpoint.cc" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751590AbcHIKQf (ORCPT ); Tue, 9 Aug 2016 06:16:35 -0400 In-Reply-To: <1470737769-30438-1-git-send-email-fw@strlen.de> Sender: netdev-owner@vger.kernel.org List-ID: Once xfrm_state_lookup_byaddr no longer acquires the state lock another cpu might be freeing the state entry at the same time. To detect this we use atomic_inc_not_zero, we then signal -EAGAIN to caller in case our result was stale. Signed-off-by: Florian Westphal --- net/xfrm/xfrm_state.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index 904ab4d..84c1db6 100644 --- a/net/xfrm/xfrm_state.c +++ b/net/xfrm/xfrm_state.c @@ -37,6 +37,11 @@ static unsigned int xfrm_state_hashmax __read_mostly = 1 * 1024 * 1024; +static inline bool xfrm_state_hold_rcu(struct xfrm_state __rcu *x) +{ + return atomic_inc_not_zero(&x->refcnt); +} + static inline unsigned int xfrm_dst_hash(struct net *net, const xfrm_address_t *daddr, const xfrm_address_t *saddr, @@ -668,7 +673,8 @@ static struct xfrm_state *__xfrm_state_lookup(struct net *net, u32 mark, if ((mark & x->mark.m) != x->mark.v) continue; - xfrm_state_hold(x); + if (!xfrm_state_hold_rcu(x)) + continue; return x; } @@ -692,7 +698,8 @@ static struct xfrm_state *__xfrm_state_lookup_byaddr(struct net *net, u32 mark, if ((mark & x->mark.m) != x->mark.v) continue; - xfrm_state_hold(x); + if (!xfrm_state_hold_rcu(x)) + continue; return x; } @@ -871,10 +878,14 @@ found: } } out: - if (x) - xfrm_state_hold(x); - else + if (x) { + if (!xfrm_state_hold_rcu(x)) { + *err = -EAGAIN; + x = NULL; + } + } else { *err = acquire_in_progress ? -EAGAIN : error; + } spin_unlock_bh(&net->xfrm.xfrm_state_lock); if (to_put) xfrm_state_put(to_put); -- 2.7.3