Skip to content

Commit

Permalink
x86/fpu: Drop_fpu() should not assume that tsk equals current
Browse files Browse the repository at this point in the history
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@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Rik 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.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
  • Loading branch information
Oleg Nesterov authored and Ingo Molnar committed Mar 13, 2015
1 parent a7c80eb commit f4c3686
Showing 1 changed file with 1 addition and 1 deletion.
2 changes: 1 addition & 1 deletion arch/x86/include/asm/fpu-internal.h
Original file line number Diff line number Diff line change
Expand Up @@ -370,7 +370,7 @@ 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();
}

Expand Down

0 comments on commit f4c3686

Please sign in to comment.