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author | Catalin Marinas <catalin.marinas@arm.com> | 2022-06-10 18:21:41 +0300 |
---|---|---|
committer | Will Deacon <will@kernel.org> | 2022-07-07 12:48:37 +0300 |
commit | 20794545c14692094a882d2221c251c4573e6adf (patch) | |
tree | 1c06ac7b159e2ccb16315df9af074082d5a8640a /arch/arm64/kernel/mte.c | |
parent | 6d05141a393071e104bf5be5ad4d0c79c6dff343 (diff) | |
download | linux-20794545c14692094a882d2221c251c4573e6adf.tar.xz |
arm64: kasan: Revert "arm64: mte: reset the page tag in page->flags"
This reverts commit e5b8d9218951e59df986f627ec93569a0d22149b.
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>
Diffstat (limited to 'arch/arm64/kernel/mte.c')
-rw-r--r-- | arch/arm64/kernel/mte.c | 9 |
1 files changed, 0 insertions, 9 deletions
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index f6b00743c399..b2b730233274 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -48,15 +48,6 @@ static void mte_sync_page_tags(struct page *page, pte_t old_pte, if (!pte_is_tagged) return; - page_kasan_tag_reset(page); - /* - * We need smp_wmb() in between setting the flags and clearing the - * tags because if another thread reads page->flags and builds a - * tagged address out of it, there is an actual dependency to the - * memory access, but on the current thread we do not guarantee that - * the new page->flags are visible before the tags were updated. - */ - smp_wmb(); mte_clear_page_tags(page_address(page)); } |