2021-03-30 16:40:08

by Andrey Konovalov

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

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 <[email protected]>
Reported-by: Sergei Trofimovich <[email protected]>
Signed-off-by: Andrey Konovalov <[email protected]>
---
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);
}

--
2.31.0.291.g576ba9dcdaf-goog

2021-03-30 16:46:01

by Vlastimil Babka

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

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 <[email protected]>
> Reported-by: Sergei Trofimovich <[email protected]>
> Signed-off-by: Andrey Konovalov <[email protected]>

Tested that the bug indeed occurs in -next and is fixed by this. Thanks.

> ---
> 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);
> }
>
>

2021-03-30 18:14:10

by Sergei Trofimovich

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

On Tue, 30 Mar 2021 18:44:09 +0200
Vlastimil Babka <[email protected]> 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 <[email protected]>
> > Reported-by: Sergei Trofimovich <[email protected]>
> > Signed-off-by: Andrey Konovalov <[email protected]>
>
> Tested that the bug indeed occurs in -next and is fixed by this. Thanks.

Reviewed-by: Sergei Trofimovich <[email protected]>

> > ---
> > 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