From: Peter Zijlstra <peterz@infradead.org>
Date: Tue, 23 Apr 2019 19:55:59 +0000 (+0200)
Subject: bpf: Fix preempt_enable_no_resched() abuse
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=0edd6b64d1939e9e9168ff27947995bb7751db5d;p=linux.git

bpf: Fix preempt_enable_no_resched() abuse

Unless the very next line is schedule(), or implies it, one must not use
preempt_enable_no_resched(). It can cause a preemption to go missing and
thereby cause arbitrary delays, breaking the PREEMPT=y invariant.

Cc: Roman Gushchin <guro@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f02367faa58db..944ccc310201d 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -510,7 +510,7 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array,
 		}					\
 _out:							\
 		rcu_read_unlock();			\
-		preempt_enable_no_resched();		\
+		preempt_enable();			\
 		_ret;					\
 	 })