On 01/29, Dave Hansen wrote: > > On 01/29/2015 01:56 PM, Oleg Nesterov wrote: > > --- x/arch/x86/kernel/traps.c > > +++ x/arch/x86/kernel/traps.c > > @@ -313,7 +313,7 @@ dotraplinkage void do_bounds(struct pt_r > > * It is not directly accessible, though, so we need to > > * do an xsave and then pull it out of the xsave buffer. > > */ > > - fpu_save_init(&tsk->thread.fpu); > > + unlazy_fpu(tsk); > > xsave_buf = &(tsk->thread.fpu.state->xsave); > ... > > bndcsr = get_xsave_addr(xsave_buf, XSTATE_BNDCSR); > > Hmm, if the the thread was not using the FPU, and this fails to save > anything in to the xsave_buf, what will bndcsr point to? It _looks_ to > me like it will just point to uninitialized data since the xsave never > happened. > > Fenghua, shouldn't get_xsave_addr() be checking the xstate bit against > the xsave->xstate_bv?
Can't really comment, but let me clarify what I meant just in case... If it was not using FPU then I guess do_bounds() can't happen. However, it can be preempted after conditional_sti(). fpu_save_init() is obviously wrong unless __thread_has_fpu() == T, and this can be false if !eagerfpu or if we add TIF_LOAD_FPU (defer FPU restore until return to userspace). Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
