* [PATCH mm] mm, kasan: fix for "integrate page_alloc init with HW_TAGS"
@ 2021-03-30 15:31 Andrey Konovalov
2021-03-30 15:54 ` Vlastimil Babka
0 siblings, 1 reply; 3+ messages in thread
From: Andrey Konovalov @ 2021-03-30 15:31 UTC (permalink / raw)
To: Andrew Morton
Cc: Vlastimil Babka, Sergei Trofimovich, Alexander Potapenko,
Marco Elver, Dmitry Vyukov, Andrey Ryabinin, Andrey Konovalov,
kasan-dev, linux-mm, linux-kernel, Andrey Konovalov
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 __GFP_ZERO allocations being incorrectly poisoned when page poisoning
is enabled.
Fix by restoring the initial order. Also add a warning comment.
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Sergei Trofimovich <slyfox@gentoo.org>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
---
mm/page_alloc.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 033bd92e8398..1fc5061f8ca1 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2328,6 +2328,12 @@ 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, a __GFP_ZERO allocation will not be initialized.
+ */
+ 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 +2344,6 @@ 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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH mm] mm, kasan: fix for "integrate page_alloc init with HW_TAGS"
2021-03-30 15:31 [PATCH mm] mm, kasan: fix for "integrate page_alloc init with HW_TAGS" Andrey Konovalov
@ 2021-03-30 15:54 ` Vlastimil Babka
2021-03-30 16:37 ` Andrey Konovalov
0 siblings, 1 reply; 3+ messages in thread
From: Vlastimil Babka @ 2021-03-30 15:54 UTC (permalink / raw)
To: Andrey Konovalov, Andrew Morton
Cc: Sergei Trofimovich, Alexander Potapenko, Marco Elver,
Dmitry Vyukov, Andrey Ryabinin, Andrey Konovalov, kasan-dev,
linux-mm, linux-kernel
On 3/30/21 5:31 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 __GFP_ZERO allocations being incorrectly poisoned when page poisoning
> is enabled.
Correction: This leads to check_poison_mem() complain about memory corruption
because the poison pattern has already been overwritten by zeroes.
> Fix by restoring the initial order. Also add a warning comment.
>
> Reported-by: Vlastimil Babka <vbabka@suse.cz>
> Reported-by: Sergei Trofimovich <slyfox@gentoo.org>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
I expect this will be folded to your patch in mmotm anyway, so the changelog is
not as important...
> ---
> mm/page_alloc.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 033bd92e8398..1fc5061f8ca1 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2328,6 +2328,12 @@ 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, a __GFP_ZERO allocation will not be initialized.
... but the comment should be corrected too:
"Otherwise, a __GFP_ZERO allocation will trigger a memory corruption report
during unpoisoning."
Thanks.
> + */
> + 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 +2344,6 @@ 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);
> }
>
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH mm] mm, kasan: fix for "integrate page_alloc init with HW_TAGS"
2021-03-30 15:54 ` Vlastimil Babka
@ 2021-03-30 16:37 ` Andrey Konovalov
0 siblings, 0 replies; 3+ messages in thread
From: Andrey Konovalov @ 2021-03-30 16:37 UTC (permalink / raw)
To: Vlastimil Babka
Cc: Andrew Morton, Sergei Trofimovich, Alexander Potapenko,
Marco Elver, Dmitry Vyukov, Andrey Ryabinin, Andrey Konovalov,
kasan-dev, Linux Memory Management List, LKML
On Tue, Mar 30, 2021 at 5:54 PM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 3/30/21 5:31 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 __GFP_ZERO allocations being incorrectly poisoned when page poisoning
> > is enabled.
>
> Correction: This leads to check_poison_mem() complain about memory corruption
> because the poison pattern has already been overwritten by zeroes.
Ah, indeed. Will send v2. Thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-03-30 15:31 [PATCH mm] mm, kasan: fix for "integrate page_alloc init with HW_TAGS" Andrey Konovalov
2021-03-30 15:54 ` Vlastimil Babka
2021-03-30 16:37 ` Andrey Konovalov
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