Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Roman Gushchin <guro@fb.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 100/114] bpf: Fix preempt_enable_no_resched() abuse
Date:   Thu, 23 May 2019 21:06:39 +0200
Message-Id: <20190523181740.223939766@linuxfoundation.org>
In-Reply-To: <20190523181731.372074275@linuxfoundation.org>
References: <20190523181731.372074275@linuxfoundation.org>
User-Agent: quilt/0.66
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

[ 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