On Wed, Nov 23, 2022 at 9:19 AM Emil Renner Berthing
<emil.renner.berthing@xxxxxxxxxxxxx> wrote:
>
> Hi Alexandre,
>
> On Mon, 21 Nov 2022 at 14:33, Alexandre Ghiti <alexghiti@xxxxxxxxxxxx> wrote:
> >
> > The EFI page table is initially created as a copy of the kernel page table.
> > With VMAP_STACK enabled, kernel stacks are allocated in the vmalloc area:
> > if the stack is allocated in a new PGD (one that was not present at the
> > moment of the efi page table creation or not synced in a previous vmalloc
> > fault), the kernel will take a trap when switching to the efi page table
> > when the vmalloc kernel stack is accessed, resulting in a kernel panic.
> >
> > Fix that by updating the efi kernel mappings before switching to the efi
> > page table.
> >
> > Signed-off-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
>
> Thanks for the patch! With this applied on the Ubuntu 5.19 kernel I
> can enable CONFIG_VMAP_STACK and cat /sys/firmware/efi/efivars/* on
> the Unmatched without locking up. So
>
> Tested-by: Emil Renner Berthing <emil.renner.berthing@xxxxxxxxxxxxx>
>
> > ---
> > arch/riscv/include/asm/efi.h | 6 +++++-
> > arch/riscv/include/asm/pgalloc.h | 11 ++++++++---
> > 2 files changed, 13 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/efi.h b/arch/riscv/include/asm/efi.h
> > index f74879a8f1ea..e229d7be4b66 100644
> > --- a/arch/riscv/include/asm/efi.h
> > +++ b/arch/riscv/include/asm/efi.h
> > @@ -10,6 +10,7 @@
> > #include <asm/mmu_context.h>
> > #include <asm/ptrace.h>
> > #include <asm/tlbflush.h>
> > +#include <asm/pgalloc.h>
> >
> > #ifdef CONFIG_EFI
> > extern void efi_init(void);
> > @@ -20,7 +21,10 @@ extern void efi_init(void);
> > int efi_create_mapping(struct mm_struct *mm, efi_memory_desc_t *md);
> > int efi_set_mapping_permissions(struct mm_struct *mm, efi_memory_desc_t *md);
> >
> > -#define arch_efi_call_virt_setup() efi_virtmap_load()
> > +#define arch_efi_call_virt_setup() ({ \
> > + sync_kernel_mappings(efi_mm.pgd); \
> > + efi_virtmap_load(); \
> > + })
> > #define arch_efi_call_virt_teardown() efi_virtmap_unload()
> >
> > #define ARCH_EFI_IRQ_FLAGS_MASK (SR_IE | SR_SPIE)
> > diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
> > index 947f23d7b6af..59dc12b5b7e8 100644
> > --- a/arch/riscv/include/asm/pgalloc.h
> > +++ b/arch/riscv/include/asm/pgalloc.h
> > @@ -127,6 +127,13 @@ static inline void p4d_free(struct mm_struct *mm, p4d_t *p4d)
> > #define __p4d_free_tlb(tlb, p4d, addr) p4d_free((tlb)->mm, p4d)
> > #endif /* __PAGETABLE_PMD_FOLDED */
> >
> > +static inline void sync_kernel_mappings(pgd_t *pgd)
> > +{
> > + memcpy(pgd + USER_PTRS_PER_PGD,
> > + init_mm.pgd + USER_PTRS_PER_PGD,
> > + (PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t));
> > +}
> > +
> > static inline pgd_t *pgd_alloc(struct mm_struct *mm)
> > {
> > pgd_t *pgd;
> > @@ -135,9 +142,7 @@ static inline pgd_t *pgd_alloc(struct mm_struct *mm)
> > if (likely(pgd != NULL)) {
> > memset(pgd, 0, USER_PTRS_PER_PGD * sizeof(pgd_t));
> > /* Copy kernel mappings */
> > - memcpy(pgd + USER_PTRS_PER_PGD,
> > - init_mm.pgd + USER_PTRS_PER_PGD,
> > - (PTRS_PER_PGD - USER_PTRS_PER_PGD) * sizeof(pgd_t));
> > + sync_kernel_mappings(pgd);
> > }
> > return pgd;
> > }
> > --
> > 2.37.2
> >
Thanks for the fix. With the correct Fixes tag in commit description:A
Reviewed-by: Atish Patra <atishp@xxxxxxxxxxxx>
--
Regards,
Atish
