On Wed, 24 Jun 2020 at 09:05, Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote:
>
> On Tue, Jun 23, 2020 at 06:59:36PM +0200, Ard Biesheuvel wrote:
> > Commit
> >
> > 84e6ffb2c49c7901 ("arm: add support for folded p4d page tables")
> >
> > updated create_mapping_late() to take folded P4Ds into account when
> > creating mappings, but inverted the p4d_alloc() failure test, resulting
> > in no mapping to be created at all.
> >
> > When the EFI rtc driver subsequently tries to invoke the EFI GetTime()
> > service, the memory regions covering the EFI data structures are missing
> > from the page tables, resulting in a crash like
> >
> > Unable to handle kernel paging request at virtual address 5ae0cf28
> > pgd = (ptrval)
> > [5ae0cf28] *pgd=80000040205003, *pmd=00000000
> > Internal error: Oops: 207 [#1] SMP THUMB2
> > Modules linked in:
> > CPU: 0 PID: 7 Comm: kworker/u32:0 Not tainted 5.7.0+ #92
> > Hardware name: QEMU KVM Virtual Machine, BIOS 0.0.0 02/06/2015
> > Workqueue: efi_rts_wq efi_call_rts
> > PC is at efi_call_rts+0x94/0x294
> > LR is at efi_call_rts+0x83/0x294
> > pc : [<c0b4f098>] lr : [<c0b4f087>] psr: 30000033
> > sp : e6219ef0 ip : 00000000 fp : ffffe000
> > r10: 00000000 r9 : 00000000 r8 : 30000013
> > r7 : e6201dd0 r6 : e6201ddc r5 : 00000000 r4 : c181f264
> > r3 : 5ae0cf10 r2 : 00000001 r1 : e6201dd0 r0 : e6201ddc
> > Flags: nzCV IRQs on FIQs on Mode SVC_32 ISA Thumb Segment none
> > Control: 70c5383d Table: 661cc840 DAC: 00000001
> > Process kworker/u32:0 (pid: 7, stack limit = 0x(ptrval))
> > ...
> > [<c0b4f098>] (efi_call_rts) from [<c0448219>] (process_one_work+0x16d/0x3d8)
> > [<c0448219>] (process_one_work) from [<c0448581>] (worker_thread+0xfd/0x408)
> > [<c0448581>] (worker_thread) from [<c044ca7b>] (kthread+0x103/0x104)
> > ...
> >
> > Fixes: 84e6ffb2c49c7901 ("arm: add support for folded p4d page tables")
> > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> > ---
> > arch/arm/mm/mmu.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> > index 628028bfbb92..bcd82614c25d 100644
> > --- a/arch/arm/mm/mmu.c
> > +++ b/arch/arm/mm/mmu.c
> > @@ -966,7 +966,7 @@ void __init create_mapping_late(struct mm_struct *mm, struct map_desc *md,
> > pud_t *pud;
> >
> > p4d = p4d_alloc(mm, pgd_offset(mm, md->virtual), md->virtual);
> > - if (!WARN_ON(!p4d))
> > + if (WARN_ON(!p4d))
>
> It must have been cosmic radiation :)
>
> Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
>
Russell,
I have put this patch into the patch system on the 24th of June, and
it fixes a guaranteed boot crash on LPAE kernels booting via EFI.
Could you please merge it as a fix?
> > return;
> > pud = pud_alloc(mm, p4d, md->virtual);
> > if (WARN_ON(!pud))
> > --
> > 2.27.0
> >
>
> --
> Sincerely yours,
> Mike.
