From: Oleg Nesterov <oleg@xxxxxxxxxx> This patch has been added to the 3.12 stable tree. If you have any objections, please let us know. =============== 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: Jiri Slaby <jslaby@xxxxxxx> --- arch/x86/include/asm/fpu-internal.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h index 5be9f879957f..18cd5ed4e1ba 100644 --- a/arch/x86/include/asm/fpu-internal.h +++ b/arch/x86/include/asm/fpu-internal.h @@ -368,7 +368,7 @@ static inline void drop_fpu(struct task_struct *tsk) preempt_disable(); tsk->fpu_counter = 0; __drop_fpu(tsk); - clear_used_math(); + clear_stopped_child_used_math(tsk); preempt_enable(); } -- 2.3.3 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html