Messages in this thread | | | Subject | Re: [PATCH v3] mm/kasan: dump alloc and free stack for page allocator | From | Vlastimil Babka <> | Date | Thu, 12 Sep 2019 16:31:42 +0200 |
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On 9/12/19 4:08 PM, Walter Wu wrote: > >> extern void __reset_page_owner(struct page *page, unsigned int order); >> diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan >> index 6c9682ce0254..dc560c7562e8 100644 >> --- a/lib/Kconfig.kasan >> +++ b/lib/Kconfig.kasan >> @@ -41,6 +41,8 @@ config KASAN_GENERIC >> select SLUB_DEBUG if SLUB >> select CONSTRUCTORS >> select STACKDEPOT >> + select PAGE_OWNER >> + select PAGE_OWNER_FREE_STACK >> help >> Enables generic KASAN mode. >> Supported in both GCC and Clang. With GCC it requires version 4.9.2 >> @@ -63,6 +65,8 @@ config KASAN_SW_TAGS >> select SLUB_DEBUG if SLUB >> select CONSTRUCTORS >> select STACKDEPOT >> + select PAGE_OWNER >> + select PAGE_OWNER_FREE_STACK >> help > > What is the difference between PAGE_OWNER+PAGE_OWNER_FREE_STACK and > DEBUG_PAGEALLOC?
Same memory usage, but debug_pagealloc means also extra checks and restricting memory access to freed pages to catch UAF.
> If you directly enable PAGE_OWNER+PAGE_OWNER_FREE_STACK > PAGE_OWNER_FREE_STACK,don't you think low-memory device to want to use > KASAN?
OK, so it should be optional? But I think it's enough to distinguish no PAGE_OWNER at all, and PAGE_OWNER+PAGE_OWNER_FREE_STACK together - I don't see much point in PAGE_OWNER only for this kind of debugging.
So how about this? KASAN wouldn't select PAGE_OWNER* but it would be recommended in the help+docs. When PAGE_OWNER and KASAN are selected by user, PAGE_OWNER_FREE_STACK gets also selected, and both will be also runtime enabled without explicit page_owner=on. I mostly want to avoid another boot-time option for enabling PAGE_OWNER_FREE_STACK. Would that be enough flexibility for low-memory devices vs full-fledged debugging?
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