On Mon, Jul 02, 2018 at 12:20:06PM +0300, Andrey Ryabinin wrote:
>
>
> On 07/02/2018 12:15 PM, Greg KH wrote:
> > On Mon, Jul 02, 2018 at 11:48:28AM +0300, Andrey Ryabinin wrote:
> >> commit 0e311d237d7f3022b7dafb639b42541bfb42fe94 upstream.
> >>
> >> When the P4D page table layer is folded at runtime, the p4d_free()
> >> should do nothing, the same as in <asm-generic/pgtable-nop4d.h>.
> >>
> >> It seems this bug should cause double-free in efi_call_phys_epilog(),
> >> but I don't know how to trigger that code path, so I can't confirm that
> >> by testing.
> >>
> >> Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
> >> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> >> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> >> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> >> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> >> Cc: stable@xxxxxxxxxxxxxxx # 4.17
> >> Fixes: 98219dda2ab5 ("x86/mm: Fold p4d page table layer at runtime")
> >> Link: http://lkml.kernel.org/r/20180625102427.15015-1-aryabinin@xxxxxxxxxxxxx
> >> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> >> Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
> >> ---
> >>
> >> Changes since v1:
> >> - Fix wrong "From:" field
> >>
> >> arch/x86/include/asm/pgalloc.h | 3 +++
> >> 1 file changed, 3 insertions(+)
> >>
> >> diff --git a/arch/x86/include/asm/pgalloc.h b/arch/x86/include/asm/pgalloc.h
> >> index 263c142a6a6c..f65e9e1cea4c 100644
> >> --- a/arch/x86/include/asm/pgalloc.h
> >> +++ b/arch/x86/include/asm/pgalloc.h
> >> @@ -184,6 +184,9 @@ static inline p4d_t *p4d_alloc_one(struct mm_struct *mm, unsigned long addr)
> >>
> >> static inline void p4d_free(struct mm_struct *mm, p4d_t *p4d)
> >> {
> >> + if (!pgtable_l5_enabled)
> >> + return;
> >> +
> >
> > Again, did you actually test-build this?
>
> Again, yes, I did test-build this.
>
> > What changed from the original
> > patch which blew the build up into little tiny pieces?
> >
>
> Removed '()'. In 4.17 pgtable_l5_enabled is variable, in 4.18 it's function.
Ah, good, it wasn't obvious that you changed anything. I'll queue this
up after these latest kernels are released in a few days.
thanks,
greg k-h
