[PATCH 5.15 096/120] riscv: Sync efi page tables kernel mappings before switching

Greg Kroah-Hartman
2022-12-05T19:40:15Z

From: Alexandre Ghiti <alexghiti@rivosinc.com>

[ Upstream commit 3f105a742725a1b78766a55169f1d827732e62b8 ]

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@rivosinc.com>
Fixes: b91540d52a08 ("RISC-V: Add EFI runtime services")
Tested-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20221121133303.1782246-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 cc4f6787f937..1bb8662875dd 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_call_virt(p, f, args...) p->f(args)
diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
index 0af6933a7100..98e040332482 100644
--- a/arch/riscv/include/asm/pgalloc.h
+++ b/arch/riscv/include/asm/pgalloc.h
@@ -38,6 +38,13 @@ static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
}
#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;
@@ -46,9 +53,7 @@ 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;
}
--
2.35.1