From 5e23fee23ea10730c752edce1777e6b7e727290f Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 2 Sep 2014 19:57:27 +0200 Subject: [PATCH] x86, fpu: copy_process: Sanitize fpu->last_cpu initialization Cosmetic, but imho memset(&dst->thread.fpu, 0) is not good simply because it hides the (important) usage of ->has_fpu/etc from grep. Change this code to initialize the members explicitly. And note that ->last_cpu = 0 looks simply wrong, this can confuse fpu_lazy_restore() if per_cpu(fpu_owner_task, 0) has already exited and copy_process() re-allocated the same task_struct. Fortunately this is not actually possible because child->fpu_counter == 0 and thus fpu_lazy_restore() will not be called, but still this is not clean/robust. Signed-off-by: Oleg Nesterov Link: http://lkml.kernel.org/r/20140902175727.GA21666@redhat.com Reviewed-by: Suresh Siddha Signed-off-by: H. Peter Anvin --- arch/x86/kernel/process.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index b9ba9d52020e..a44268c897bd 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -66,7 +66,9 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) { *dst = *src; - memset(&dst->thread.fpu, 0, sizeof(dst->thread.fpu)); + dst->thread.fpu.has_fpu = 0; + dst->thread.fpu.last_cpu = ~0; + dst->thread.fpu.state = NULL; if (tsk_used_math(src)) { int err = fpu_alloc(&dst->thread.fpu); if (err)