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authorCong Wang <xiyou.wangcong@gmail.com>2019-01-31 13:05:49 -0800
committerSteffen Klassert <steffen.klassert@secunet.com>2019-02-05 06:29:20 +0100
commitf75a2804da391571563c4b6b29e7797787332673 (patch)
treeab0938d51019534539a0e2585cca20a82f8557af /net/xfrm
parent09db51241118aeb06e1c8cd393b45879ce099b36 (diff)
downloadlinux-f75a2804da391571563c4b6b29e7797787332673.tar.bz2
xfrm: destroy xfrm_state synchronously on net exit path
xfrm_state_put() moves struct xfrm_state to the GC list and schedules the GC work to clean it up. On net exit call path, xfrm_state_flush() is called to clean up and xfrm_flush_gc() is called to wait for the GC work to complete before exit. However, this doesn't work because one of the ->destructor(), ipcomp_destroy(), schedules the same GC work again inside the GC work. It is hard to wait for such a nested async callback. This is also why syzbot still reports the following warning: WARNING: CPU: 1 PID: 33 at net/ipv6/xfrm6_tunnel.c:351 xfrm6_tunnel_net_exit+0x2cb/0x500 net/ipv6/xfrm6_tunnel.c:351 ... ops_exit_list.isra.0+0xb0/0x160 net/core/net_namespace.c:153 cleanup_net+0x51d/0xb10 net/core/net_namespace.c:551 process_one_work+0xd0c/0x1ce0 kernel/workqueue.c:2153 worker_thread+0x143/0x14a0 kernel/workqueue.c:2296 kthread+0x357/0x430 kernel/kthread.c:246 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352 In fact, it is perfectly fine to bypass GC and destroy xfrm_state synchronously on net exit call path, because it is in process context and doesn't need a work struct to do any blocking work. This patch introduces xfrm_state_put_sync() which simply bypasses GC, and lets its callers to decide whether to use this synchronous version. On net exit path, xfrm_state_fini() and xfrm6_tunnel_net_exit() use it. And, as ipcomp_destroy() itself is blocking, it can use xfrm_state_put_sync() directly too. Also rename xfrm_state_gc_destroy() to ___xfrm_state_destroy() to reflect this change. Fixes: b48c05ab5d32 ("xfrm: Fix warning in xfrm6_tunnel_net_exit.") Reported-and-tested-by: syzbot+e9aebef558e3ed673934@syzkaller.appspotmail.com Cc: Steffen Klassert <steffen.klassert@secunet.com> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Diffstat (limited to 'net/xfrm')
-rw-r--r--net/xfrm/xfrm_state.c30
-rw-r--r--net/xfrm/xfrm_user.c2
2 files changed, 20 insertions, 12 deletions
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 23c92891758a..1bb971f46fc6 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -432,7 +432,7 @@ void xfrm_state_free(struct xfrm_state *x)
}
EXPORT_SYMBOL(xfrm_state_free);
-static void xfrm_state_gc_destroy(struct xfrm_state *x)
+static void ___xfrm_state_destroy(struct xfrm_state *x)
{
tasklet_hrtimer_cancel(&x->mtimer);
del_timer_sync(&x->rtimer);
@@ -474,7 +474,7 @@ static void xfrm_state_gc_task(struct work_struct *work)
synchronize_rcu();
hlist_for_each_entry_safe(x, tmp, &gc_list, gclist)
- xfrm_state_gc_destroy(x);
+ ___xfrm_state_destroy(x);
}
static enum hrtimer_restart xfrm_timer_handler(struct hrtimer *me)
@@ -598,14 +598,19 @@ struct xfrm_state *xfrm_state_alloc(struct net *net)
}
EXPORT_SYMBOL(xfrm_state_alloc);
-void __xfrm_state_destroy(struct xfrm_state *x)
+void __xfrm_state_destroy(struct xfrm_state *x, bool sync)
{
WARN_ON(x->km.state != XFRM_STATE_DEAD);
- spin_lock_bh(&xfrm_state_gc_lock);
- hlist_add_head(&x->gclist, &xfrm_state_gc_list);
- spin_unlock_bh(&xfrm_state_gc_lock);
- schedule_work(&xfrm_state_gc_work);
+ if (sync) {
+ synchronize_rcu();
+ ___xfrm_state_destroy(x);
+ } else {
+ spin_lock_bh(&xfrm_state_gc_lock);
+ hlist_add_head(&x->gclist, &xfrm_state_gc_list);
+ spin_unlock_bh(&xfrm_state_gc_lock);
+ schedule_work(&xfrm_state_gc_work);
+ }
}
EXPORT_SYMBOL(__xfrm_state_destroy);
@@ -708,7 +713,7 @@ xfrm_dev_state_flush_secctx_check(struct net *net, struct net_device *dev, bool
}
#endif
-int xfrm_state_flush(struct net *net, u8 proto, bool task_valid)
+int xfrm_state_flush(struct net *net, u8 proto, bool task_valid, bool sync)
{
int i, err = 0, cnt = 0;
@@ -730,7 +735,10 @@ restart:
err = xfrm_state_delete(x);
xfrm_audit_state_delete(x, err ? 0 : 1,
task_valid);
- xfrm_state_put(x);
+ if (sync)
+ xfrm_state_put_sync(x);
+ else
+ xfrm_state_put(x);
if (!err)
cnt++;
@@ -2215,7 +2223,7 @@ void xfrm_state_delete_tunnel(struct xfrm_state *x)
if (atomic_read(&t->tunnel_users) == 2)
xfrm_state_delete(t);
atomic_dec(&t->tunnel_users);
- xfrm_state_put(t);
+ xfrm_state_put_sync(t);
x->tunnel = NULL;
}
}
@@ -2375,8 +2383,8 @@ void xfrm_state_fini(struct net *net)
unsigned int sz;
flush_work(&net->xfrm.state_hash_work);
- xfrm_state_flush(net, IPSEC_PROTO_ANY, false);
flush_work(&xfrm_state_gc_work);
+ xfrm_state_flush(net, IPSEC_PROTO_ANY, false, true);
WARN_ON(!list_empty(&net->xfrm.state_all));
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index c6d26afcf89d..a131f9ff979e 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1932,7 +1932,7 @@ static int xfrm_flush_sa(struct sk_buff *skb, struct nlmsghdr *nlh,
struct xfrm_usersa_flush *p = nlmsg_data(nlh);
int err;
- err = xfrm_state_flush(net, p->proto, true);
+ err = xfrm_state_flush(net, p->proto, true, false);
if (err) {
if (err == -ESRCH) /* empty table */
return 0;