From: Jiang Liu <jiang.liu@huawei.com>
Date: Fri, 27 Sep 2013 08:04:41 +0000 (+0100)
Subject: arm64: fix possible invalid FPSIMD initialization state
X-Git-Tag: firefly_0821_release~3680^2~36^2~55^2~4
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=2f36c2ef1393d17dd2dde3458a55f804e0c10eac;p=firefly-linux-kernel-4.4.55.git

arm64: fix possible invalid FPSIMD initialization state

If context switching happens during executing fpsimd_flush_thread(),
stale value in FPSIMD registers will be saved into current thread's
fpsimd_state by fpsimd_thread_switch(). That may cause invalid
initialization state for the new process, so disable preemption
when executing fpsimd_flush_thread().

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Cc: Jiang Liu <liuj97@gmail.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 6db83cea1c975b9a102e17def7d2795814e1ae2b)
Signed-off-by: Mark Brown <broonie@linaro.org>
---

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 1f2e4d5a5c0f..bb785d23dbde 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -80,8 +80,10 @@ void fpsimd_thread_switch(struct task_struct *next)
 
 void fpsimd_flush_thread(void)
 {
+	preempt_disable();
 	memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
 	fpsimd_load_state(&current->thread.fpsimd_state);
+	preempt_enable();
 }
 
 #ifdef CONFIG_KERNEL_MODE_NEON