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x86/fpu: Change math_error() to use unlazy_fpu(), kill (now) unused save_init_fpu() 

math_error() calls save_init_fpu() after conditional_sti(), this means
that the caller can be preempted. If !use_eager_fpu() we can hit the
WARN_ON_ONCE(!__thread_has_fpu(tsk)) and/or save the wrong FPU state.

Change math_error() to use unlazy_fpu() and kill save_init_fpu().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1423252925-14451-4-git-send-email-riel@redhat.com
Signed-off-by: Borislav Petkov <bp@suse.de>
This commit is contained in:
Oleg Nesterov 2015-02-06 15:02:00 -05:00 committed by Borislav Petkov
parent 1a2a7f4ec8
commit 08a744c6bf
2 changed files with 1 additions and 19 deletions
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18
arch/x86/include/asm/fpu-internal.h
View File

@ -517,24 +517,6 @@ static inline void __save_fpu(struct task_struct *tsk)
fpu_fxsave(&tsk->thread.fpu);
}
/*
* These disable preemption on their own and are safe
*/
static inline void save_init_fpu(struct task_struct *tsk)
{
WARN_ON_ONCE(!__thread_has_fpu(tsk));
if (use_eager_fpu()) {
__save_fpu(tsk);
return;
}
preempt_disable();
__save_init_fpu(tsk);
__thread_fpu_end(tsk);
preempt_enable();
}
/*
* i387 state interaction
*/

2
arch/x86/kernel/traps.c
View File

@ -663,7 +663,7 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr)
/*
* Save the info for the exception handler and clear the error.
*/
save_init_fpu(task);
unlazy_fpu(task);
task->thread.trap_nr = trapnr;
task->thread.error_code = error_code;
info.si_signo = SIGFPE;