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 > -- > Regards/Gruss, > Boris. > > Good mailing practices for 400: avoid top-posting and trim the reply.
