linux/debian/patches-rt/0175-x86-fpu-Disable-preemption-around-local_bh_disable.patch

From a8a5de903659159f5de58c8a0bc4dffbe6bc2f44 Mon Sep 17 00:00:00 2001
Message-Id: <a8a5de903659159f5de58c8a0bc4dffbe6bc2f44.1599166691.git.zanussi@kernel.org>
In-Reply-To: <56457dc415803c8abc5acb513ada877a79596f05.1599166690.git.zanussi@kernel.org>
References: <56457dc415803c8abc5acb513ada877a79596f05.1599166690.git.zanussi@kernel.org>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Tue, 11 Dec 2018 15:10:33 +0100
Subject: [PATCH 175/333] x86/fpu: Disable preemption around local_bh_disable()
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.142-rt63.tar.xz

__fpu__restore_sig() restores the content of the FPU state in the CPUs
and in order to avoid concurency it disbles BH. On !RT it also disables
preemption but on RT we can get preempted in BH.

Add preempt_disable() while the FPU state is restored.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/x86/kernel/fpu/signal.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index d99a8ee9e185..5e0274a94133 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -344,10 +344,12 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
 			sanitize_restored_xstate(tsk, &env, xfeatures, fx_only);
 		}
 
+		preempt_disable();
 		local_bh_disable();
 		fpu->initialized = 1;
 		fpu__restore(fpu);
 		local_bh_enable();
+		preempt_enable();
 
 		return err;
 	} else {
-- 
2.17.1