[PATCH 3.10 122/129] arm64: fix possible invalid FPSIMD initialization state

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jiang Liu <jiang.liu@xxxxxxxxxx>

commit 6db83cea1c975b9a102e17def7d2795814e1ae2b upstream.

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@xxxxxxxxxx>
Cc: Jiang Liu <liuj97@xxxxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 arch/arm64/kernel/fpsimd.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -79,8 +79,10 @@ void fpsimd_thread_switch(struct task_st
 
 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();
 }
 
 /*


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