On 02/28/2017 02:04 AM, Mark Rutland wrote: > On Tue, Feb 28, 2017 at 08:42:51AM +0000, Ard Biesheuvel wrote: >> (+ Mark) > > (+ Laura) > >> On 28 February 2017 at 07:05, Miles Chen <miles.c...@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 > > I don't have strong feelings either way. > > This isn't typically enabled, and it's under debugfs, so this shouldn't > be accessible by a typical user anyhow. > > That said, there are very few of us who need to take a look at this > file. I'm happy to deal with attacking kptr_restrict when required. >
In the interest of security it's probably for the best to switch to the restricted pointer. Who knows what might get enabled or forgotten about. I don't like the idea of tying enablement of the file to kptr_restrict though. This should probably be fixed up on all arches that implement the page table dump feature. Laura > Thanks, > Mark. > >>> ---[ 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.c...@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 >>> >>> >>> _______________________________________________ >>> linux-arm-kernel mailing list >>> linux-arm-ker...@lists.infradead.org >>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel