linux-kernel - [patch] x86, i387: fix ptrace leakage using init

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Date:	Mon, 3 Mar 2008 13:01:08 -0800
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	mingo@...e.hu, hpa@...or.com, tglx@...utronix.de
Cc:	linux-kernel@...r.kernel.org, roland@...hat.com
Subject: [patch] x86, i387: fix ptrace leakage using init_fpu()

This needs to go into 2.6.25. Thanks.
---

This bug is introduced by the recent i387 merge.

Current usage of unlazy_fpu() in ptrace specific routines is wrong. unlazy_fpu()
will not init fpu if the task never used math. So the ptrace calls
can expose the parent tasks FPU data in some cases.

Replace it with the init_fpu() which will init the math state, if the task
never used math before.

Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
---

diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c
index 763dfc4..60fe801 100644
--- a/arch/x86/kernel/i387.c
+++ b/arch/x86/kernel/i387.c
@@ -132,7 +132,7 @@ int xfpregs_get(struct task_struct *target, const struct user_regset *regset,
 	if (!cpu_has_fxsr)
 		return -ENODEV;
 
-	unlazy_fpu(target);
+	init_fpu(target);
 
 	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
 				   &target->thread.i387.fxsave, 0, -1);
@@ -147,7 +147,7 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset,
 	if (!cpu_has_fxsr)
 		return -ENODEV;
 
-	unlazy_fpu(target);
+	init_fpu(target);
 	set_stopped_child_used_math(target);
 
 	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
@@ -307,7 +307,7 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset,
 	if (!HAVE_HWFP)
 		return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf);
 
-	unlazy_fpu(target);
+	init_fpu(target);
 
 	if (!cpu_has_fxsr)
 		return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
@@ -332,7 +332,7 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset,
 	if (!HAVE_HWFP)
 		return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf);
 
-	unlazy_fpu(target);
+	init_fpu(target);
 	set_stopped_child_used_math(target);
 
 	if (!cpu_has_fxsr)
--
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