Messages in this thread | | | Date | Tue, 16 Aug 2022 13:04:00 +0200 | Subject | Re: [PATCH 5.19 0767/1157] kasan: fix zeroing vmalloc memory with HW_TAGS | From | Jiri Slaby <> |
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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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