riscv: mm: Ensure prot of VM_WRITE and VM_EXEC must be readable

Commit 8aeb7b17f04e ("RISC-V: Make mmap() with PROT_WRITE imply PROT_READ")
allows riscv to use mmap with PROT_WRITE only, and meanwhile mmap with w+x
is also permitted. However, when userspace tries to access this page with
PROT_WRITE|PROT_EXEC, which causes infinite loop at load page fault as
well as it triggers soft lockup. According to riscv privileged spec,
"Writable pages must also be marked readable". The fix to drop the
`PAGE_COPY_READ_EXEC` and then `PAGE_COPY_EXEC` would be just used instead.
This aligns the other arches (i.e arm64) for protection_map.

Fixes: 8aeb7b17f04e ("RISC-V: Make mmap() with PROT_WRITE imply PROT_READ")
Signed-off-by: Hsieh-Tseng Shen <woodrow.shen@sifive.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20230425102828.1616812-1-woodrow.shen@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 2258b27..75970ee 100644 (file)
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -165,8 +165,7 @@ extern struct pt_alloc_ops pt_ops __initdata;
                                         _PAGE_EXEC | _PAGE_WRITE)
 
 #define PAGE_COPY              PAGE_READ
-#define PAGE_COPY_EXEC         PAGE_EXEC
-#define PAGE_COPY_READ_EXEC    PAGE_READ_EXEC
+#define PAGE_COPY_EXEC         PAGE_READ_EXEC
 #define PAGE_SHARED            PAGE_WRITE
 #define PAGE_SHARED_EXEC       PAGE_WRITE_EXEC
 

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index c6bb966..0fe75c9 100644 (file)
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -293,7 +293,7 @@ static const pgprot_t protection_map[16] = {
        [VM_EXEC]                                       = PAGE_EXEC,
        [VM_EXEC | VM_READ]                             = PAGE_READ_EXEC,
        [VM_EXEC | VM_WRITE]                            = PAGE_COPY_EXEC,
-       [VM_EXEC | VM_WRITE | VM_READ]                  = PAGE_COPY_READ_EXEC,
+       [VM_EXEC | VM_WRITE | VM_READ]                  = PAGE_COPY_EXEC,
        [VM_SHARED]                                     = PAGE_NONE,
        [VM_SHARED | VM_READ]                           = PAGE_READ,
        [VM_SHARED | VM_WRITE]                          = PAGE_SHARED,