(+ Mike)
On Fri, 30 Oct 2020 at 03:25, Florian Fainelli <f.fainelli@xxxxxxxxx> wrote:
>
>
>
> On 10/29/2020 4:14 AM, Ard Biesheuvel wrote:
> > On Thu, 29 Oct 2020 at 12:03, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
> >>
> >> free_highpages() iterates over the free memblock regions in high
> >> memory, and marks each page as available for the memory management
> >> system. However, as it rounds the end of each region downwards, we
> >> may end up freeing a page that is memblock_reserve()d, resulting
> >> in memory corruption. So align the end of the range to the next
> >> page instead.
> >>
> >> Cc: <stable@xxxxxxxxxxxxxxx>
> >> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> >> ---
> >> arch/arm/mm/init.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> >> index a391804c7ce3..d41781cb5496 100644
> >> --- a/arch/arm/mm/init.c
> >> +++ b/arch/arm/mm/init.c
> >> @@ -354,7 +354,7 @@ static void __init free_highpages(void)
> >> for_each_free_mem_range(i, NUMA_NO_NODE, MEMBLOCK_NONE,
> >> &range_start, &range_end, NULL) {
> >> unsigned long start = PHYS_PFN(range_start);
> >> - unsigned long end = PHYS_PFN(range_end);
> >> + unsigned long end = PHYS_PFN(PAGE_ALIGN(range_end));
> >>
> >
> > Apologies, this should be
> >
> > - unsigned long start = PHYS_PFN(range_start);
> > + unsigned long start = PHYS_PFN(PAGE_ALIGN(range_start));
> > unsigned long end = PHYS_PFN(range_end);
> >
> >
> > Strangely enough, the wrong version above also fixed the issue I was
> > seeing, but it is start that needs rounding up, not end.
>
> Is there a particular commit that you identified which could be used as
> Fixes: tag to ease the back porting of such a change?
Ah hold on. This appears to be a very recent regression, in
cddb5ddf2b76debdb8cad1728ad0a9321383d933, added in v5.10-rc1.
The old code was
unsigned long start = memblock_region_memory_base_pfn(mem);
which uses PFN_UP() to round up, whereas the new code rounds down.
Looks like this is broken on a lot of platforms.
Mike?
