Re: [PATCH mm v2] mm, kasan: fix for "integrate page_alloc init with HW_TAGS"

[Sergei Trofimovich]

On Tue, 30 Mar 2021 18:44:09 +0200
Vlastimil Babka <vbabka@xxxxxxx> wrote:

> On 3/30/21 6:37 PM, Andrey Konovalov wrote:
> > My commit "integrate page_alloc init with HW_TAGS" changed the order of
> > kernel_unpoison_pages() and kernel_init_free_pages() calls. This leads
> > to complaints from the page unpoisoning code, as the poison pattern gets
> > overwritten for __GFP_ZERO allocations.
> > 
> > Fix by restoring the initial order. Also add a warning comment.
> > 
> > Reported-by: Vlastimil Babka <vbabka@xxxxxxx>
> > Reported-by: Sergei Trofimovich <slyfox@xxxxxxxxxx>
> > Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>  
> 
> Tested that the bug indeed occurs in -next and is fixed by this. Thanks.

Reviewed-by: Sergei Trofimovich <slyfox@xxxxxxxxxx>

> > ---
> >  mm/page_alloc.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index 033bd92e8398..d2c020563c0b 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -2328,6 +2328,13 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
> >  	arch_alloc_page(page, order);
> >  	debug_pagealloc_map_pages(page, 1 << order);
> >  
> > +	/*
> > +	 * Page unpoisoning must happen before memory initialization.
> > +	 * Otherwise, the poison pattern will be overwritten for __GFP_ZERO
> > +	 * allocations and the page unpoisoning code will complain.
> > +	 */
> > +	kernel_unpoison_pages(page, 1 << order);
> > +
> >  	/*
> >  	 * As memory initialization might be integrated into KASAN,
> >  	 * kasan_alloc_pages and kernel_init_free_pages must be
> > @@ -2338,7 +2345,6 @@ inline void post_alloc_hook(struct page *page, unsigned int order,
> >  	if (init && !kasan_has_integrated_init())
> >  		kernel_init_free_pages(page, 1 << order);
> >  
> > -	kernel_unpoison_pages(page, 1 << order);
> >  	set_page_owner(page, order, gfp_flags);
> >  }
> >  
> >   
> 


-- 

  Sergei