linux-kernel - [PATCH v2 2/7] x86, fpu: __restore_xstate_sig()->math_state_restore() needs preempt

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Message-ID: <20140902175717.GA21649@redhat.com>
Date:	Tue, 2 Sep 2014 19:57:17 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"H. Peter Anvin" <hpa@...or.com>,
	Suresh Siddha <sbsiddha@...il.com>
Cc:	Al Viro <viro@...IV.linux.org.uk>,
	Bean Anderson <bean@...lsystems.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Ingo Molnar <mingo@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/7] x86, fpu:
	__restore_xstate_sig()->math_state_restore() needs preempt_disable()

Add preempt_disable() + preempt_enable() around math_state_restore() in
__restore_xstate_sig(). Otherwise __switch_to() after __thread_fpu_begin()
can overwrite fpu->state we are going to restore.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Cc: stable@...r.kernel.org
Reviewed-by: Suresh Siddha <sbsiddha@...il.com>
---
 arch/x86/kernel/xsave.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
index 74b34c2..dd50e26 100644
--- a/arch/x86/kernel/xsave.c
+++ b/arch/x86/kernel/xsave.c
@@ -397,8 +397,11 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size)
 			set_used_math();
 		}
 
-		if (use_eager_fpu())
+		if (use_eager_fpu()) {
+			preempt_disable();
 			math_state_restore();
+			preempt_enable();
+		}
 
 		return err;
 	} else {
-- 
1.5.5.1

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