* Andy Lutomirski <[email protected]> wrote: > On Fri, Nov 24, 2017 at 10:25 AM, Borislav Petkov <[email protected]> wrote: > > On Fri, Nov 24, 2017 at 06:23:40PM +0100, Ingo Molnar wrote: > >> From: Andy Lutomirski <[email protected]> > >> > >> When we start using an entry trampoline, a #GP from userspace will > >> be delivered on the entry stack, not on the task stack. Fix the > >> espfix64 #DF fixup to set up #GP according to TSS.SP0, rather than > >> assuming that pt_regs + 1 == SP0. This won't change anything > >> without an entry stack, but it will make the code continue to work > >> when an entry stack is added. > >> > >> Signed-off-by: Andy Lutomirski <[email protected]> > >> Signed-off-by: Thomas Gleixner <[email protected]> > >> Reviewed-by: Thomas Gleixner <[email protected]> > >> Cc: Borislav Petkov <[email protected]> > >> Cc: Brian Gerst <[email protected]> > >> Cc: Dave Hansen <[email protected]> > >> Cc: Josh Poimboeuf <[email protected]> > >> Cc: Linus Torvalds <[email protected]> > >> Cc: Peter Zijlstra <[email protected]> > >> Link: > >> https://lkml.kernel.org/r/b1ef4136616c6bd2a75d1fd2736d1d54437d65a8.1511497875.git.l...@kernel.org > >> Signed-off-by: Ingo Molnar <[email protected]> > >> --- > >> arch/x86/kernel/traps.c | 5 +++-- > >> 1 file changed, 3 insertions(+), 2 deletions(-) > >> > >> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > >> index 2008dd0f8ccb..1bd43f044c62 100644 > >> --- a/arch/x86/kernel/traps.c > >> +++ b/arch/x86/kernel/traps.c > >> @@ -359,7 +359,8 @@ dotraplinkage void do_double_fault(struct pt_regs > >> *regs, long error_code) > >> regs->cs == __KERNEL_CS && > >> regs->ip == (unsigned long)native_irq_return_iret) > >> { > >> - struct pt_regs *normal_regs = task_pt_regs(current); > >> + struct pt_regs *normal_regs = > >> + (struct pt_regs *)this_cpu_read(cpu_tss.x86_tss.sp0) > >> - 1; > > > > Just let that line stick out. Also, you can shorten it by renaming > > normal_regs to something much shorter - it is a local variable and the > > comment already explains everything you you can just as well have: > > > > struct pt_regs *r = (struct pt_regs > > *)this_cpu_read(cpu_tss.x86_tss.sp0) - 1; > > > > Done, along with much better comments. > > https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/entry_stack&id=6510485d026abdd144d170b1bc8508327acb5648
I have added Boris's reviewed-by tag: Reviewed-by: Borislav Petkov <[email protected]> which I suspect applies now? Thanks, Ingo
