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authorFrederic Weisbecker <frederic@kernel.org>2021-06-28 15:34:28 +0200
committerSteffen Klassert <steffen.klassert@secunet.com>2021-07-02 09:27:55 +0200
commit2580d3f40022642452dd8422bfb8c22e54cf84bb (patch)
tree0c10c26a6d4bb8f398b40de983894a02bd13f7f1
parenteaf228263921cd15962654b539d916380a0f076e (diff)
xfrm: Fix RCU vs hash_resize_mutex lock inversion
xfrm_bydst_resize() calls synchronize_rcu() while holding hash_resize_mutex. But then on PREEMPT_RT configurations, xfrm_policy_lookup_bytype() may acquire that mutex while running in an RCU read side critical section. This results in a deadlock. In fact the scope of hash_resize_mutex is way beyond the purpose of xfrm_policy_lookup_bytype() to just fetch a coherent and stable policy for a given destination/direction, along with other details. The lower level net->xfrm.xfrm_policy_lock, which among other things protects per destination/direction references to policy entries, is enough to serialize and benefit from priority inheritance against the write side. As a bonus, it makes it officially a per network namespace synchronization business where a policy table resize on namespace A shouldn't block a policy lookup on namespace B. Fixes: 77cc278f7b20 (xfrm: policy: Use sequence counters with associated lock) Cc: stable@vger.kernel.org Cc: Ahmed S. Darwish <a.darwish@linutronix.de> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Varad Gautam <varad.gautam@suse.com> Cc: Steffen Klassert <steffen.klassert@secunet.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: David S. Miller <davem@davemloft.net> Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
-rw-r--r--include/net/netns/xfrm.h1
-rw-r--r--net/xfrm/xfrm_policy.c17
2 files changed, 9 insertions, 9 deletions
diff --git a/include/net/netns/xfrm.h b/include/net/netns/xfrm.h
index e816b6a3ef2b..9b376b87bd54 100644
--- a/include/net/netns/xfrm.h
+++ b/include/net/netns/xfrm.h
@@ -74,6 +74,7 @@ struct netns_xfrm {
#endif
spinlock_t xfrm_state_lock;
seqcount_spinlock_t xfrm_state_hash_generation;
+ seqcount_spinlock_t xfrm_policy_hash_generation;
spinlock_t xfrm_policy_lock;
struct mutex xfrm_cfg_mutex;
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index ce500f847b99..46a6d15b66d6 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -155,7 +155,6 @@ static struct xfrm_policy_afinfo const __rcu *xfrm_policy_afinfo[AF_INET6 + 1]
__read_mostly;
static struct kmem_cache *xfrm_dst_cache __ro_after_init;
-static __read_mostly seqcount_mutex_t xfrm_policy_hash_generation;
static struct rhashtable xfrm_policy_inexact_table;
static const struct rhashtable_params xfrm_pol_inexact_params;
@@ -585,7 +584,7 @@ static void xfrm_bydst_resize(struct net *net, int dir)
return;
spin_lock_bh(&net->xfrm.xfrm_policy_lock);
- write_seqcount_begin(&xfrm_policy_hash_generation);
+ write_seqcount_begin(&net->xfrm.xfrm_policy_hash_generation);
odst = rcu_dereference_protected(net->xfrm.policy_bydst[dir].table,
lockdep_is_held(&net->xfrm.xfrm_policy_lock));
@@ -596,7 +595,7 @@ static void xfrm_bydst_resize(struct net *net, int dir)
rcu_assign_pointer(net->xfrm.policy_bydst[dir].table, ndst);
net->xfrm.policy_bydst[dir].hmask = nhashmask;
- write_seqcount_end(&xfrm_policy_hash_generation);
+ write_seqcount_end(&net->xfrm.xfrm_policy_hash_generation);
spin_unlock_bh(&net->xfrm.xfrm_policy_lock);
synchronize_rcu();
@@ -1245,7 +1244,7 @@ static void xfrm_hash_rebuild(struct work_struct *work)
} while (read_seqretry(&net->xfrm.policy_hthresh.lock, seq));
spin_lock_bh(&net->xfrm.xfrm_policy_lock);
- write_seqcount_begin(&xfrm_policy_hash_generation);
+ write_seqcount_begin(&net->xfrm.xfrm_policy_hash_generation);
/* make sure that we can insert the indirect policies again before
* we start with destructive action.
@@ -1354,7 +1353,7 @@ static void xfrm_hash_rebuild(struct work_struct *work)
out_unlock:
__xfrm_policy_inexact_flush(net);
- write_seqcount_end(&xfrm_policy_hash_generation);
+ write_seqcount_end(&net->xfrm.xfrm_policy_hash_generation);
spin_unlock_bh(&net->xfrm.xfrm_policy_lock);
mutex_unlock(&hash_resize_mutex);
@@ -2095,9 +2094,9 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type,
rcu_read_lock();
retry:
do {
- sequence = read_seqcount_begin(&xfrm_policy_hash_generation);
+ sequence = read_seqcount_begin(&net->xfrm.xfrm_policy_hash_generation);
chain = policy_hash_direct(net, daddr, saddr, family, dir);
- } while (read_seqcount_retry(&xfrm_policy_hash_generation, sequence));
+ } while (read_seqcount_retry(&net->xfrm.xfrm_policy_hash_generation, sequence));
ret = NULL;
hlist_for_each_entry_rcu(pol, chain, bydst) {
@@ -2128,7 +2127,7 @@ static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type,
}
skip_inexact:
- if (read_seqcount_retry(&xfrm_policy_hash_generation, sequence))
+ if (read_seqcount_retry(&net->xfrm.xfrm_policy_hash_generation, sequence))
goto retry;
if (ret && !xfrm_pol_hold_rcu(ret))
@@ -4084,6 +4083,7 @@ static int __net_init xfrm_net_init(struct net *net)
/* Initialize the per-net locks here */
spin_lock_init(&net->xfrm.xfrm_state_lock);
spin_lock_init(&net->xfrm.xfrm_policy_lock);
+ seqcount_spinlock_init(&net->xfrm.xfrm_policy_hash_generation, &net->xfrm.xfrm_policy_lock);
mutex_init(&net->xfrm.xfrm_cfg_mutex);
rv = xfrm_statistics_init(net);
@@ -4128,7 +4128,6 @@ void __init xfrm_init(void)
{
register_pernet_subsys(&xfrm_net_ops);
xfrm_dev_init();
- seqcount_mutex_init(&xfrm_policy_hash_generation, &hash_resize_mutex);
xfrm_input_init();
#ifdef CONFIG_XFRM_ESPINTCP