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    SubjectRe: [PATCH 5.19 0767/1157] kasan: fix zeroing vmalloc memory with HW_TAGS
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    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]



    > + }
    > +}
    > +
    > void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
    > kasan_vmalloc_flags_t flags)
    > {
    > u8 tag;
    > unsigned long redzone_start, redzone_size;
    >
    > - if (!kasan_vmalloc_enabled())
    > - return (void *)start;
    > -
    > - if (!is_vmalloc_or_module_addr(start))
    > + if (!kasan_vmalloc_enabled() || !is_vmalloc_or_module_addr(start)) {
    > + if (flags & KASAN_VMALLOC_INIT)
    > + init_vmalloc_pages(start, size);
    > return (void *)start;
    > + }
    >
    > /*
    > - * Skip unpoisoning and assigning a pointer tag for non-VM_ALLOC
    > - * mappings as:
    > + * Don't tag non-VM_ALLOC mappings, as:
    > *
    > * 1. Unlike the software KASAN modes, hardware tag-based KASAN only
    > * supports tagging physical memory. Therefore, it can only tag a
    > * single mapping of normal physical pages.
    > * 2. Hardware tag-based KASAN can only tag memory mapped with special
    > - * mapping protection bits, see arch_vmalloc_pgprot_modify().
    > + * mapping protection bits, see arch_vmap_pgprot_tagged().
    > * As non-VM_ALLOC mappings can be mapped outside of vmalloc code,
    > * providing these bits would require tracking all non-VM_ALLOC
    > * mappers.
    > @@ -289,15 +299,19 @@ void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
    > *
    > * For non-VM_ALLOC allocations, page_alloc memory is tagged as usual.
    > */
    > - if (!(flags & KASAN_VMALLOC_VM_ALLOC))
    > + if (!(flags & KASAN_VMALLOC_VM_ALLOC)) {
    > + WARN_ON(flags & KASAN_VMALLOC_INIT);
    > return (void *)start;
    > + }
    >
    > /*
    > * Don't tag executable memory.
    > * The kernel doesn't tolerate having the PC register tagged.
    > */
    > - if (!(flags & KASAN_VMALLOC_PROT_NORMAL))
    > + if (!(flags & KASAN_VMALLOC_PROT_NORMAL)) {
    > + WARN_ON(flags & KASAN_VMALLOC_INIT);
    > return (void *)start;
    > + }
    >
    > tag = kasan_random_tag();
    > start = set_tag(start, tag);
    > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
    > index effd1ff6a4b4..a1ab9b472571 100644
    > --- a/mm/vmalloc.c
    > +++ b/mm/vmalloc.c
    > @@ -3168,15 +3168,15 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
    >
    > /*
    > * Mark the pages as accessible, now that they are mapped.
    > - * The init condition should match the one in post_alloc_hook()
    > - * (except for the should_skip_init() check) to make sure that memory
    > - * is initialized under the same conditions regardless of the enabled
    > - * KASAN mode.
    > + * The condition for setting KASAN_VMALLOC_INIT should complement the
    > + * one in post_alloc_hook() with regards to the __GFP_SKIP_ZERO check
    > + * to make sure that memory is initialized under the same conditions.
    > * Tag-based KASAN modes only assign tags to normal non-executable
    > * allocations, see __kasan_unpoison_vmalloc().
    > */
    > kasan_flags |= KASAN_VMALLOC_VM_ALLOC;
    > - if (!want_init_on_free() && want_init_on_alloc(gfp_mask))
    > + if (!want_init_on_free() && want_init_on_alloc(gfp_mask) &&
    > + (gfp_mask & __GFP_SKIP_ZERO))
    > kasan_flags |= KASAN_VMALLOC_INIT;
    > /* KASAN_VMALLOC_PROT_NORMAL already set if required. */
    > area->addr = kasan_unpoison_vmalloc(area->addr, real_size, kasan_flags);

    --
    js
    suse labs

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