Commit 1b6bd919 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Sasha Levin

x86/fpu: Drop_fpu() should not assume that tsk equals current

[ Upstream commit f4c36863 ]

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: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Cc: <stable@vger.kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pekka Riikonen <priikone@iki.fi>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: Suresh Siddha <sbsiddha@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150309171041.GB11388@redhat.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarSasha Levin <sasha.levin@oracle.com>
parent 1a29c27a
......@@ -368,7 +368,7 @@ static inline void drop_fpu(struct task_struct *tsk)
preempt_disable();
tsk->thread.fpu_counter = 0;
__drop_fpu(tsk);
clear_used_math();
clear_stopped_child_used_math(tsk);
preempt_enable();
}
......
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