[PATCH] riscv: Fix W+X mapping warning

[Atish Patra]

On Wed, Nov 11, 2020 at 10:44 PM Kefeng Wang <wangkefeng.wang at huawei.com> wrote:
>
> When boot with DEBUG_WX triggers the WX warning,
>   riscv/mm: Found insecure W+X mapping at address ffffffe000000000/0xffffffe000000000
>   WARNING: CPU: 1 PID: 1 at arch/riscv/mm/ptdump.c:236 note_page+0x248/0x25a
>   ...
>   Checked W+X mappings: failed, 512 W+X pages found
>
> The kernel_page_tables shows first 2M(kernel image) is with W attribute,
> Use _start instead of text_start in mark_rodata_ro().
>
> Before,
> 0xffffffe000000000-0xffffffe000200000    0x0000000080200000         2M PMD     D A . . X W R V
> 0xffffffe000200000-0xffffffe000a00000    0x0000000080400000         8M PMD     D A . . X . R V
> 0xffffffe000a00000-0xffffffe001000000    0x0000000080c00000         6M PMD     D A . . . . R V
> 0xffffffe001000000-0xffffffe17fe00000    0x0000000081200000      6126M PMD     D A . . . W R V
>
> After,
> 0xffffffe000000000-0xffffffe000a00000    0x0000000080200000        10M PMD     D A . . X . R V
> 0xffffffe000a00000-0xffffffe001000000    0x0000000080c00000         6M PMD     D A . . . . R V
> 0xffffffe001000000-0xffffffe17fe00000    0x0000000081200000      6126M PMD     D A . . . W R V
>

This is already fixed by the following series.
https://patchwork.kernel.org/project/linux-riscv/list/?series=377843

> Signed-off-by: Kefeng Wang <wangkefeng.wang at huawei.com>
> ---
>  arch/riscv/mm/init.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 1d330bde9cf1..d739a46d9fc4 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -624,13 +624,13 @@ static inline void setup_vm_final(void)
>  #ifdef CONFIG_STRICT_KERNEL_RWX
>  void mark_rodata_ro(void)
>  {
> -       unsigned long text_start = (unsigned long)_text;
> +       unsigned long start = (unsigned long)_start;
>         unsigned long text_end = (unsigned long)_etext;
>         unsigned long rodata_start = (unsigned long)__start_rodata;
>         unsigned long data_start = (unsigned long)_data;
>         unsigned long max_low = (unsigned long)(__va(PFN_PHYS(max_low_pfn)));
>
> -       set_memory_ro(text_start, (text_end - text_start) >> PAGE_SHIFT);
> +       set_memory_ro(start, (text_end - start) >> PAGE_SHIFT);
>         set_memory_ro(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT);
>         set_memory_nx(rodata_start, (data_start - rodata_start) >> PAGE_SHIFT);
>         set_memory_nx(data_start, (max_low - data_start) >> PAGE_SHIFT);
> --
> 2.26.2
>
>
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-- 
Regards,
Atish