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SubjectRe: [PATCH] x86/entry/64: Fix CR3 restore order in paranoid_exit()

* Dave Hansen <dave.hansen@intel.com> wrote:

> On 02/13/2018 06:27 PM, Josh Poimboeuf wrote:
> > --- a/arch/x86/entry/entry_64.S
> > +++ b/arch/x86/entry/entry_64.S
> > @@ -1167,10 +1167,10 @@ ENTRY(paranoid_exit)
> > UNWIND_HINT_REGS
> > DISABLE_INTERRUPTS(CLBR_ANY)
> > TRACE_IRQS_OFF_DEBUG
> > + RESTORE_CR3 scratch_reg=%r15 save_reg=%r14
> > testl %ebx, %ebx /* swapgs needed? */
> > jnz .Lparanoid_exit_no_swapgs
> > TRACE_IRQS_IRETQ
> > - RESTORE_CR3 scratch_reg=%rbx save_reg=%r14
> > SWAPGS_UNSAFE_STACK
> > jmp .Lparanoid_exit_restore
> > .Lparanoid_exit_no_swapgs:
>
> TRACE_IRQS_* call non-entry functions that are not mapped by the user
> CR3. How can this possibly work? What am I missing?

How about something like the patch below? (Totally untested)

Thanks,

Ingo
---
arch/x86/entry/entry_64.S | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index cd216c9431e1..8971bd64d515 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1175,6 +1175,7 @@ ENTRY(paranoid_exit)
jmp .Lparanoid_exit_restore
.Lparanoid_exit_no_swapgs:
TRACE_IRQS_IRETQ_DEBUG
+ RESTORE_CR3 scratch_reg=%rbx save_reg=%r14
.Lparanoid_exit_restore:
jmp restore_regs_and_return_to_kernel
END(paranoid_exit)
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