Messages in this thread | | | Date | Tue, 16 Aug 2022 13:14:13 +0200 | Subject | Re: [PATCH 5.19 0767/1157] kasan: fix zeroing vmalloc memory with HW_TAGS | From | Jiri Slaby <> |
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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
>> + } >> +} >> + >> 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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