arm64: kasan: Revert "arm64: mte: reset the page tag in page->flags"
This reverts commit e5b8d921. Pages mapped in user-space with PROT_MTE have the allocation tags either zeroed or copied/restored to some user values. In order for the kernel to access such pages via page_address(), resetting the tag in page->flags was necessary. This tag resetting was deferred to set_pte_at() -> mte_sync_page_tags() but it can race with another CPU reading the flags (via page_to_virt()): P0 (mte_sync_page_tags): P1 (memcpy from virt_to_page): Rflags!=0xff Wflags=0xff DMB (doesn't help) Wtags=0 Rtags=0 // fault Since now the post_alloc_hook() function resets the page->flags tag when unpoisoning is skipped for user pages (including the __GFP_ZEROTAGS case), revert the arm64 commit calling page_kasan_tag_reset(). Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Peter Collingbourne <pcc@google.com> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Acked-by: Andrey Konovalov <andreyknvl@gmail.com> Link: https://lore.kernel.org/r/20220610152141.2148929-5-catalin.marinas@arm.comSigned-off-by: Will Deacon <will@kernel.org>
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