Messages in this thread | | | From | Pavel Tatashin <> | Date | Mon, 15 Feb 2021 08:42:17 -0500 | Subject | Re: [PATCH] arm64: mm: correct the start of physical address in linear map |
| |
On Mon, Feb 15, 2021 at 12:26 AM Anshuman Khandual <anshuman.khandual@arm.com> wrote: > > Hello Pavel, > > On 2/13/21 6:53 AM, Pavel Tatashin wrote: > > Memory hotplug may fail on systems with CONFIG_RANDOMIZE_BASE because the > > linear map range is not checked correctly. > > > > The start physical address that linear map covers can be actually at the > > end of the range because of randmomization. Check that and if so reduce it > > to 0. > > Looking at the code, this seems possible if memstart_addr which is a signed > value becomes large (after falling below 0) during arm64_memblock_init().
Right.
> > > > > This can be verified on QEMU with setting kaslr-seed to ~0ul: > > > > memstart_offset_seed = 0xffff > > START: __pa(_PAGE_OFFSET(vabits_actual)) = ffff9000c0000000 > > END: __pa(PAGE_END - 1) = 1000bfffffff > > > > Signed-off-by: Pavel Tatashin <pasha.tatashin@soleen.com> > > Fixes: 58284a901b42 ("arm64/mm: Validate hotplug range before creating linear mapping") > > --- > > arch/arm64/mm/mmu.c | 15 +++++++++++++-- > > 1 file changed, 13 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > > index ae0c3d023824..6057ecaea897 100644 > > --- a/arch/arm64/mm/mmu.c > > +++ b/arch/arm64/mm/mmu.c > > @@ -1444,14 +1444,25 @@ static void __remove_pgd_mapping(pgd_t *pgdir, unsigned long start, u64 size) > > > > static bool inside_linear_region(u64 start, u64 size) > > { > > + u64 start_linear_pa = __pa(_PAGE_OFFSET(vabits_actual)); > > + u64 end_linear_pa = __pa(PAGE_END - 1); > > + > > + /* > > + * Check for a wrap, it is possible because of randomized linear mapping > > + * the start physical address is actually bigger than the end physical > > + * address. In this case set start to zero because [0, end_linear_pa] > > + * range must still be able to cover all addressable physical addresses. > > + */ > > If this is possible only with randomized linear mapping, could you please > add IS_ENABLED(CONFIG_RANDOMIZED_BASE) during the switch over. Wondering > if WARN_ON(start_linear_pa > end_linear_pa) should be added otherwise i.e > when linear mapping randomization is not enabled.
Yeah, good idea, I will add ifdef for CONFIG_RANDOMIZED_BASE.
> > > + if (start_linear_pa > end_linear_pa) > > + start_linear_pa = 0; > > This looks okay but will double check and give it some more testing.
Thank you, Pasha
| |