[PATCH] arm64: dump: hide kernel pointers

[Ard Biesheuvel]

(+ Mark)

On 28 February 2017 at 07:05, Miles Chen <miles.chen at mediatek.com> wrote:
> Mask kernel pointers of /sys/kernel/debug/kernel_page_tables entry like
> /proc/vmallocinfo does.
>
> With sysctl kernel.kptr_restrict=0 or 1:
> cat /sys/kernel/debug/kernel_page_tables

I wonder if this file should be accessible at all if kptr_restrict > 0

> ---[ Modules start ]---
> ---[ Modules end ]---
> ---[ vmalloc() Area ]---
> ffffff8008000000-ffffff8008010000          64K PTE       RW NX SHD AF...
> ffffff8008015000-ffffff8008016000           4K PTE       RW NX SHD AF...
> ffffff8008020000-ffffff8008030000          64K PTE       RW NX SHD AF...
> ffffff8008031000-ffffff8008071000         256K PTE       RW NX SHD AF...
> ffffff8008080000-ffffff8008200000        1536K PTE       ro x  SHD AF...
> ffffff8008200000-ffffff8008400000           2M PMD       ro x  SHD AF...
> ffffff8008400000-ffffff8008540000        1280K PTE       ro x  SHD AF...
> ffffff8008540000-ffffff8008690000        1344K PTE       ro NX SHD AF...
> ffffff8008940000-ffffff8008a10000         832K PTE       RW NX SHD AF...
> ffffff8008aca000-ffffff8008acd000          12K PTE       RW NX SHD AF...
> ffffffbebffd8000-ffffffbebffdb000          12K PTE       RW NX SHD AF...
> ---[ vmalloc() End ]---
> ---[ Fixmap start ]---
> ffffffbefe800000-ffffffbefea00000           2M PMD       ro NX SHD AF...
> ---[ Fixmap end ]---
> ---[ PCI I/O start ]---
> ---[ PCI I/O end ]---
> ---[ Linear Mapping ]---
> ffffffc000000000-ffffffc000080000         512K PTE       RW NX SHD AF...
> ffffffc000080000-ffffffc000200000        1536K PTE       ro NX SHD AF...
> ffffffc000200000-ffffffc000600000           4M PMD       ro NX SHD AF...
> ffffffc000600000-ffffffc000690000         576K PTE       ro NX SHD AF...
> ffffffc000690000-ffffffc000800000        1472K PTE       RW NX SHD AF...
> ffffffc000800000-ffffffc002000000          24M PMD       RW NX SHD AF...
> ffffffc002000000-ffffffc040000000         992M PMD       RW NX SHD AF...
> ffffffc040000000-ffffffc080000000           1G PGD       RW NX SHD AF...
>
> With sysctl kernel.kptr_restrict=2:
> cat /sys/kernel/debug/kernel_page_tables
> ---[ Modules start ]---
> ---[ Modules end ]---
> ---[ vmalloc() Area ]---
> 0000000000000000-0000000000000000          64K PTE       RW NX SHD AF...
> 0000000000000000-0000000000000000           4K PTE       RW NX SHD AF...
> 0000000000000000-0000000000000000          64K PTE       RW NX SHD AF...
> 0000000000000000-0000000000000000         256K PTE       RW NX SHD AF...
> 0000000000000000-0000000000000000        1536K PTE       ro x  SHD AF...
> 0000000000000000-0000000000000000           2M PMD       ro x  SHD AF...
> 0000000000000000-0000000000000000        1280K PTE       ro x  SHD AF...
> 0000000000000000-0000000000000000        1344K PTE       ro NX SHD AF...
> 0000000000000000-0000000000000000         832K PTE       RW NX SHD AF...
> 0000000000000000-0000000000000000          12K PTE       RW NX SHD AF...
> 0000000000000000-0000000000000000          12K PTE       RW NX SHD AF...
> ---[ vmalloc() End ]---
> ---[ Fixmap start ]---
> 0000000000000000-0000000000000000           2M PMD       ro NX SHD AF...
> ---[ Fixmap end ]---
> ---[ PCI I/O start ]---
> ---[ PCI I/O end ]---
> ---[ Linear Mapping ]---
> 0000000000000000-0000000000000000         512K PTE       RW NX SHD AF...
> 0000000000000000-0000000000000000        1536K PTE       ro NX SHD AF...
> 0000000000000000-0000000000000000           4M PMD       ro NX SHD AF...
> 0000000000000000-0000000000000000         576K PTE       ro NX SHD AF...
> 0000000000000000-0000000000000000        1472K PTE       RW NX SHD AF...
> 0000000000000000-0000000000000000          24M PMD       RW NX SHD AF...
> 0000000000000000-0000000000000000         992M PMD       RW NX SHD AF...
> 0000000000000000-0000000000000000           1G PGD       RW NX SHD AF...
>
> Signed-off-by: Miles Chen <miles.chen at mediatek.com>
> ---
>  arch/arm64/mm/dump.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/mm/dump.c b/arch/arm64/mm/dump.c
> index ca74a2a..e055ecf 100644
> --- a/arch/arm64/mm/dump.c
> +++ b/arch/arm64/mm/dump.c
> @@ -253,8 +253,8 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
>                 if (st->current_prot) {
>                         note_prot_uxn(st, addr);
>                         note_prot_wx(st, addr);
> -                       pt_dump_seq_printf(st->seq, "0x%016lx-0x%016lx   ",
> -                                  st->start_address, addr);
> +                       pt_dump_seq_printf(st->seq, "%pK-%pK   ",
> +                                  (void *)st->start_address, (void *)addr);
>
>                         delta = (addr - st->start_address) >> 10;
>                         while (!(delta & 1023) && unit[1]) {
> --
> 1.9.1
>
>
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