netdev - [PATCH net-next 1/2] bpf: don't enable preemption twice in smap_do

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Message-Id: <d90eed71c2a723edd75f19fb1b921fec74d8a514.1502983087.git.daniel@iogearbox.net>
Date:   Thu, 17 Aug 2017 17:22:36 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     davem@...emloft.net
Cc:     john.fastabend@...il.com, ast@...com, netdev@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH net-next 1/2] bpf: don't enable preemption twice in smap_do_verdict

In smap_do_verdict(), the fall-through branch leads to call
preempt_enable() twice for the SK_REDIRECT, which creates an
imbalance. Only enable it for all remaining cases again.

Fixes: 174a79ff9515 ("bpf: sockmap with sk redirect support")
Reported-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
---
 kernel/bpf/sockmap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index f7e5e6c..39de541 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -135,7 +135,8 @@ static void smap_do_verdict(struct smap_psock *psock, struct sk_buff *skb)
 	/* Fall through and free skb otherwise */
 	case SK_DROP:
 	default:
-		preempt_enable();
+		if (rc != SK_REDIRECT)
+			preempt_enable();
 		kfree_skb(skb);
 	}
 }
-- 
1.9.3