This is a note to let you know that I've just added the patch titled
x86/fpu: Drop_fpu() should not assume that tsk equals current
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-fpu-drop_fpu-should-not-assume-that-tsk-equals-current.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From f4c3686386393c120710dd34df2a74183ab805fd Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Date: Fri, 13 Mar 2015 09:53:10 +0100
Subject: x86/fpu: Drop_fpu() should not assume that tsk equals current
From: Oleg Nesterov <oleg@xxxxxxxxxx>
commit f4c3686386393c120710dd34df2a74183ab805fd upstream.
drop_fpu() does clear_used_math() and usually this is correct
because tsk == current.
However switch_fpu_finish()->restore_fpu_checking() is called before
__switch_to() updates the "current_task" variable. If it fails,
we will wrongly clear the PF_USED_MATH flag of the previous task.
So use clear_stopped_child_used_math() instead.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Pekka Riikonen <priikone@xxxxxx>
Cc: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
Cc: Suresh Siddha <sbsiddha@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20150309171041.GB11388@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/fpu-internal.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/x86/include/asm/fpu-internal.h
+++ b/arch/x86/include/asm/fpu-internal.h
@@ -370,7 +370,7 @@ static inline void drop_fpu(struct task_
preempt_disable();
tsk->fpu_counter = 0;
__drop_fpu(tsk);
- clear_used_math();
+ clear_stopped_child_used_math(tsk);
preempt_enable();
}
Patches currently in stable-queue which might be from oleg@xxxxxxxxxx are
queue-3.10/x86-fpu-drop_fpu-should-not-assume-that-tsk-equals-current.patch
queue-3.10/x86-fpu-avoid-math_state_restore-without-used_math-in-__restore_xstate_sig.patch
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