[PATCH AUTOSEL 4.19 18/25] bpf: Fix preempt_enable_no_resched() abuse

* [PATCH AUTOSEL 4.19 18/25] bpf: Fix preempt_enable_no_resched() abuse
       [not found] <20190516114029.8682-1-sashal@kernel.org>
@ 2019-05-16 11:40 ` Sasha Levin
  0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2019-05-16 11:40 UTC (permalink / raw)
  To: linux-kernel, stable
  Cc: Peter Zijlstra, Roman Gushchin, Alexei Starovoitov,
	Daniel Borkmann, Sasha Levin, netdev, bpf

From: Peter Zijlstra <peterz@infradead.org>

[ Upstream commit 0edd6b64d1939e9e9168ff27947995bb7751db5d ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/bpf.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 523481a3471b5..fd95f2efe5f32 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -400,7 +400,7 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array,
 		}					\
 _out:							\
 		rcu_read_unlock();			\
-		preempt_enable_no_resched();		\
+		preempt_enable();			\
 		_ret;					\
 	 })
 
-- 
2.20.1


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