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20794545c1
This reverts commit e5b8d92189.
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.com
Signed-off-by: Will Deacon <will@kernel.org>
38 lines
868 B
C
38 lines
868 B
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Based on arch/arm/mm/copypage.c
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*
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* Copyright (C) 2002 Deep Blue Solutions Ltd, All Rights Reserved.
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* Copyright (C) 2012 ARM Ltd.
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*/
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#include <linux/bitops.h>
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#include <linux/mm.h>
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#include <asm/page.h>
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#include <asm/cacheflush.h>
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#include <asm/cpufeature.h>
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#include <asm/mte.h>
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void copy_highpage(struct page *to, struct page *from)
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{
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void *kto = page_address(to);
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void *kfrom = page_address(from);
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copy_page(kto, kfrom);
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if (system_supports_mte() && test_bit(PG_mte_tagged, &from->flags)) {
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set_bit(PG_mte_tagged, &to->flags);
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mte_copy_page_tags(kto, kfrom);
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}
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}
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EXPORT_SYMBOL(copy_highpage);
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void copy_user_highpage(struct page *to, struct page *from,
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unsigned long vaddr, struct vm_area_struct *vma)
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{
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copy_highpage(to, from);
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flush_dcache_page(to);
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}
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EXPORT_SYMBOL_GPL(copy_user_highpage);
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