| Message ID | 24cd7db274090f0e5bc3adcdc7399243668e3171.1614987311.git.andreyknvl@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC | expand |
On Sat, 6 Mar 2021 00:36:33 +0100 Andrey Konovalov <andreyknvl@google.com> wrote: > Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called > after debug_pagealloc_unmap_pages(). This causes a crash when > debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an > unmapped page. > > This patch puts kasan_free_nondeferred_pages() before > debug_pagealloc_unmap_pages() and arch_free_page(), which can also make > the page unavailable. > > ... > > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1304,6 +1304,12 @@ static __always_inline bool free_pages_prepare(struct page *page, > > kernel_poison_pages(page, 1 << order); > > + /* > + * With hardware tag-based KASAN, memory tags must be set before the > + * page becomes unavailable via debug_pagealloc or arch_free_page. > + */ > + kasan_free_nondeferred_pages(page, order, fpi_flags); > + > /* > * arch_free_page() can make the page's contents inaccessible. s390 > * does this. So nothing which can access the page's contents should > @@ -1313,8 +1319,6 @@ static __always_inline bool free_pages_prepare(struct page *page, > > debug_pagealloc_unmap_pages(page, 1 << order); > > - kasan_free_nondeferred_pages(page, order, fpi_flags); > - > return true; > } kasan_free_nondeferred_pages() has only two args in current mainline. I fixed that in the obvious manner...
On Sat, Mar 6, 2021 at 12:50 AM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Sat, 6 Mar 2021 00:36:33 +0100 Andrey Konovalov <andreyknvl@google.com> wrote: > > > Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called > > after debug_pagealloc_unmap_pages(). This causes a crash when > > debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an > > unmapped page. > > > > This patch puts kasan_free_nondeferred_pages() before > > debug_pagealloc_unmap_pages() and arch_free_page(), which can also make > > the page unavailable. > > > > ... > > > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1304,6 +1304,12 @@ static __always_inline bool free_pages_prepare(struct page *page, > > > > kernel_poison_pages(page, 1 << order); > > > > + /* > > + * With hardware tag-based KASAN, memory tags must be set before the > > + * page becomes unavailable via debug_pagealloc or arch_free_page. > > + */ > > + kasan_free_nondeferred_pages(page, order, fpi_flags); > > + > > /* > > * arch_free_page() can make the page's contents inaccessible. s390 > > * does this. So nothing which can access the page's contents should > > @@ -1313,8 +1319,6 @@ static __always_inline bool free_pages_prepare(struct page *page, > > > > debug_pagealloc_unmap_pages(page, 1 << order); > > > > - kasan_free_nondeferred_pages(page, order, fpi_flags); > > - > > return true; > > } > > kasan_free_nondeferred_pages() has only two args in current mainline. Ah, yes, forgot to mention: this goes on top of: kasan: initialize shadow to TAG_INVALID for SW_TAGS mm, kasan: don't poison boot memory with tag-based modes > > I fixed that in the obvious manner... Thanks! If you changed this patch, you'll also need to change the other one though.
On Sat, Mar 6, 2021 at 12:54 AM Andrey Konovalov <andreyknvl@google.com> wrote: > > On Sat, Mar 6, 2021 at 12:50 AM Andrew Morton <akpm@linux-foundation.org> wrote: > > > > On Sat, 6 Mar 2021 00:36:33 +0100 Andrey Konovalov <andreyknvl@google.com> wrote: > > > > > Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called > > > after debug_pagealloc_unmap_pages(). This causes a crash when > > > debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an > > > unmapped page. > > > > > > This patch puts kasan_free_nondeferred_pages() before > > > debug_pagealloc_unmap_pages() and arch_free_page(), which can also make > > > the page unavailable. > > > > > > ... > > > > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -1304,6 +1304,12 @@ static __always_inline bool free_pages_prepare(struct page *page, > > > > > > kernel_poison_pages(page, 1 << order); > > > > > > + /* > > > + * With hardware tag-based KASAN, memory tags must be set before the > > > + * page becomes unavailable via debug_pagealloc or arch_free_page. > > > + */ > > > + kasan_free_nondeferred_pages(page, order, fpi_flags); > > > + > > > /* > > > * arch_free_page() can make the page's contents inaccessible. s390 > > > * does this. So nothing which can access the page's contents should > > > @@ -1313,8 +1319,6 @@ static __always_inline bool free_pages_prepare(struct page *page, > > > > > > debug_pagealloc_unmap_pages(page, 1 << order); > > > > > > - kasan_free_nondeferred_pages(page, order, fpi_flags); > > > - > > > return true; > > > } > > > > kasan_free_nondeferred_pages() has only two args in current mainline. > > Ah, yes, forgot to mention: this goes on top of: > > kasan: initialize shadow to TAG_INVALID for SW_TAGS > mm, kasan: don't poison boot memory with tag-based modes > > > > > I fixed that in the obvious manner... > > Thanks! > > If you changed this patch, you'll also need to change the other one though. Nevermind, just realized that this should be a backportable fix :)
On Sat, 6 Mar 2021 00:54:32 +0100 Andrey Konovalov <andreyknvl@google.com> wrote: > On Sat, Mar 6, 2021 at 12:50 AM Andrew Morton <akpm@linux-foundation.org> wrote: > > > > On Sat, 6 Mar 2021 00:36:33 +0100 Andrey Konovalov <andreyknvl@google.com> wrote: > > > > > Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called > > > after debug_pagealloc_unmap_pages(). This causes a crash when > > > debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an > > > unmapped page. > > > > > > This patch puts kasan_free_nondeferred_pages() before > > > debug_pagealloc_unmap_pages() and arch_free_page(), which can also make > > > the page unavailable. > > > > > > ... > > > > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -1304,6 +1304,12 @@ static __always_inline bool free_pages_prepare(struct page *page, > > > > > > kernel_poison_pages(page, 1 << order); > > > > > > + /* > > > + * With hardware tag-based KASAN, memory tags must be set before the > > > + * page becomes unavailable via debug_pagealloc or arch_free_page. > > > + */ > > > + kasan_free_nondeferred_pages(page, order, fpi_flags); > > > + > > > /* > > > * arch_free_page() can make the page's contents inaccessible. s390 > > > * does this. So nothing which can access the page's contents should > > > @@ -1313,8 +1319,6 @@ static __always_inline bool free_pages_prepare(struct page *page, > > > > > > debug_pagealloc_unmap_pages(page, 1 << order); > > > > > > - kasan_free_nondeferred_pages(page, order, fpi_flags); > > > - > > > return true; > > > } > > > > kasan_free_nondeferred_pages() has only two args in current mainline. > > Ah, yes, forgot to mention: this goes on top of: > > kasan: initialize shadow to TAG_INVALID for SW_TAGS > mm, kasan: don't poison boot memory with tag-based modes This patch (kasan, mm: fix crash with HW_TAGS and DEBUG_PAGEALLOC) is cc:stable, so it should come head of the other two lower priority patches. > > > > I fixed that in the obvious manner... > > Thanks! > > If you changed this patch, you'll also need to change the other one though. Yup.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 969e7012fce0..0efb07b5907c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1304,6 +1304,12 @@ static __always_inline bool free_pages_prepare(struct page *page, kernel_poison_pages(page, 1 << order); + /* + * With hardware tag-based KASAN, memory tags must be set before the + * page becomes unavailable via debug_pagealloc or arch_free_page. + */ + kasan_free_nondeferred_pages(page, order, fpi_flags); + /* * arch_free_page() can make the page's contents inaccessible. s390 * does this. So nothing which can access the page's contents should @@ -1313,8 +1319,6 @@ static __always_inline bool free_pages_prepare(struct page *page, debug_pagealloc_unmap_pages(page, 1 << order); - kasan_free_nondeferred_pages(page, order, fpi_flags); - return true; }
Currently, kasan_free_nondeferred_pages()->kasan_free_pages() is called after debug_pagealloc_unmap_pages(). This causes a crash when debug_pagealloc is enabled, as HW_TAGS KASAN can't set tags on an unmapped page. This patch puts kasan_free_nondeferred_pages() before debug_pagealloc_unmap_pages() and arch_free_page(), which can also make the page unavailable. Fixes: 94ab5b61ee16 ("kasan, arm64: enable CONFIG_KASAN_HW_TAGS") Cc: <stable@vger.kernel.org> Signed-off-by: Andrey Konovalov <andreyknvl@google.com> --- Changes v1->v2: - Move kasan_free_nondeferred_pages() before arch_free_page(). --- mm/page_alloc.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)