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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+e149f7d1328c26f9c12f@syzkaller.appspotmail.com,
        Florian Westphal <fw@strlen.de>,
        Steffen Klassert <steffen.klassert@secunet.com>
Subject: [PATCH 4.14 009/159] xfrm: dont call xfrm_policy_cache_flush while holding spinlock
Date:   Fri, 23 Feb 2018 19:25:17 +0100
Message-Id: <20180223170744.323363188@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Westphal <fw@strlen.de>

commit b1bdcb59b64f806ef08d25a85c39ffb3ad841ce6 upstream.

xfrm_policy_cache_flush can sleep, so it cannot be called while holding
a spinlock.  We could release the lock first, but I don't see why we need
to invoke this function here in first place, the packet path won't reuse
an xdst entry unless its still valid.

While at it, add an annotation to xfrm_policy_cache_flush, it would
have probably caught this bug sooner.

Fixes: ec30d78c14a813 ("xfrm: add xdst pcpu cache")
Reported-by: syzbot+e149f7d1328c26f9c12f@syzkaller.appspotmail.com
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/xfrm/xfrm_policy.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -975,8 +975,6 @@ int xfrm_policy_flush(struct net *net, u
 	}
 	if (!cnt)
 		err = -ESRCH;
-	else
-		xfrm_policy_cache_flush();
 out:
 	spin_unlock_bh(&net->xfrm.xfrm_policy_lock);
 	return err;
@@ -1738,6 +1736,8 @@ void xfrm_policy_cache_flush(void)
 	bool found = 0;
 	int cpu;
 
+	might_sleep();
+
 	local_bh_disable();
 	rcu_read_lock();
 	for_each_possible_cpu(cpu) {