Patch "riscv: Sync efi page table's kernel mappings before switching" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    riscv: Sync efi page table's kernel mappings before switching

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     riscv-sync-efi-page-table-s-kernel-mappings-before-s.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 309a70fdc593c39652d53e29effdfc8de757dd9d
Author: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Date:   Mon Nov 21 14:33:03 2022 +0100

    riscv: Sync efi page table's kernel mappings before switching
    
    [ 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@xxxxxxxxxxxx>
    Fixes: b91540d52a08 ("RISC-V: Add EFI runtime services")
    Tested-by: Emil Renner Berthing <emil.renner.berthing@xxxxxxxxxxxxx>
    Reviewed-by: Atish Patra <atishp@xxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20221121133303.1782246-1-alexghiti@xxxxxxxxxxxx
    Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

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;
 }