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/4bc503537efdc539ffc3f461c1b70162eea31cf6.165479851... 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); + } +} + 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 cadfbb5155ea..06c555fc5be0 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3170,15 +3170,15 @@ 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);