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[3.11,131/208] arm64: fix possible invalid FPSIMD initialization state

Message ID 1389628849-1614-132-git-send-email-luis.henriques@canonical.com
State New
Headers show

Commit Message

Luis Henriques Jan. 13, 2014, 3:59 p.m. UTC 
3.11.10.3 -stable review patch.  If anyone has any objections, please let me know.

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

From: Jiang Liu <jiang.liu@huawei.com>

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@huawei.com>
Cc: Jiang Liu <liuj97@gmail.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
 arch/arm64/kernel/fpsimd.c | 2 ++
 1 file changed, 2 insertions(+)
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Patch

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index e8b8357..2fa308e 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -79,8 +79,10 @@  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();
 }
 
 /*