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    SubjectRe: [PATCH 5.19 0767/1157] kasan: fix zeroing vmalloc memory with HW_TAGS
    On Tue, Aug 16, 2022 at 01:14:13PM +0200, Jiri Slaby wrote:
    > On 16. 08. 22, 13:04, Jiri Slaby wrote:
    > > On 15. 08. 22, 20:02, Greg Kroah-Hartman wrote:
    > > > From: Andrey Konovalov <andreyknvl@google.com>
    > > >
    > > > [ Upstream commit 6c2f761dad7851d8088b91063ccaea3c970efe78 ]
    > > >
    > > > HW_TAGS KASAN skips zeroing page_alloc allocations backing vmalloc
    > > > mappings via __GFP_SKIP_ZERO.  Instead, these pages are zeroed via
    > > > kasan_unpoison_vmalloc() by passing the KASAN_VMALLOC_INIT flag.
    > > >
    > > > The problem is that __kasan_unpoison_vmalloc() does not zero pages when
    > > > either kasan_vmalloc_enabled() or is_vmalloc_or_module_addr() fail.
    > > >
    > > > Thus:
    > > >
    > > > 1. Change __vmalloc_node_range() to only set KASAN_VMALLOC_INIT when
    > > >     __GFP_SKIP_ZERO is set.
    > > >
    > > > 2. Change __kasan_unpoison_vmalloc() to always zero pages when the
    > > >     KASAN_VMALLOC_INIT flag is set.
    > > >
    > > > 3. Add WARN_ON() asserts to check that KASAN_VMALLOC_INIT cannot be set
    > > >     in other early return paths of __kasan_unpoison_vmalloc().
    > > >
    > > > Also clean up the comment in __kasan_unpoison_vmalloc.
    > > >
    > > > Link: https://lkml.kernel.org/r/4bc503537efdc539ffc3f461c1b70162eea31cf6.1654798516.git.andreyknvl@google.com
    > > > Fixes: 23689e91fb22 ("kasan, vmalloc: add vmalloc tagging for HW_TAGS")
    > > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
    > > > Cc: Marco Elver <elver@google.com>
    > > > Cc: Alexander Potapenko <glider@google.com>
    > > > Cc: Dmitry Vyukov <dvyukov@google.com>
    > > > Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
    > > > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    > > > Signed-off-by: Sasha Levin <sashal@kernel.org>
    > > > ---
    > > >   mm/kasan/hw_tags.c | 32 +++++++++++++++++++++++---------
    > > >   mm/vmalloc.c       | 10 +++++-----
    > > >   2 files changed, 28 insertions(+), 14 deletions(-)
    > > >
    > > > diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
    > > > index 9e1b6544bfa8..9ad8eff71b28 100644
    > > > --- a/mm/kasan/hw_tags.c
    > > > +++ b/mm/kasan/hw_tags.c
    > > > @@ -257,27 +257,37 @@ static void unpoison_vmalloc_pages(const void
    > > > *addr, u8 tag)
    > > >       }
    > > >   }
    > > > +static void init_vmalloc_pages(const void *start, unsigned long size)
    > > > +{
    > > > +    const void *addr;
    > > > +
    > > > +    for (addr = start; addr < start + size; addr += PAGE_SIZE) {
    > > > +        struct page *page = virt_to_page(addr);
    > > > +
    > > > +        clear_highpage_kasan_tagged(page);
    > >
    > > This breaks build on aarch64:
    > > > mm/kasan/hw_tags.c: In function 'init_vmalloc_pages':
    > > > mm/kasan/hw_tags.c:267:17: error: implicit declaration of function
    > > > 'clear_highpage_kasan_tagged'
    > > > [-Werror=implicit-function-declaration]
    >
    > Which translates into: this is missing:
    > commit d9da8f6cf55eeca642c021912af1890002464c64
    > Author: Andrey Konovalov <andreyknvl@gmail.com>
    > Date: Thu Jun 9 20:18:46 2022 +0200
    >
    > mm: introduce clear_highpage_kasan_tagged

    Thanks, now added to both 5.18.y and 5.19.y. I'll push out some -rc2
    releases with this in it so it can get some testing.

    greg k-h

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