diff options
| author | Catalin Marinas <catalin.marinas@arm.com> | 2022-06-10 16:21:41 +0100 |
|---|---|---|
| committer | Will Deacon <will@kernel.org> | 2022-07-07 10:48:37 +0100 |
| commit | 20794545c14692094a882d2221c251c4573e6adf (patch) | |
| tree | 1c06ac7b159e2ccb16315df9af074082d5a8640a /arch/arm64/mm | |
| parent | 6d05141a393071e104bf5be5ad4d0c79c6dff343 (diff) | |
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/mm')
| -rw-r--r-- | arch/arm64/mm/copypage.c | 9 | ||||
| -rw-r--r-- | arch/arm64/mm/mteswap.c | 9 |
2 files changed, 0 insertions, 18 deletions
diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c index 0dea80bf6de4..24913271e898 100644 --- a/arch/arm64/mm/copypage.c +++ b/arch/arm64/mm/copypage.c @@ -23,15 +23,6 @@ void copy_highpage(struct page *to, struct page *from) if (system_supports_mte() && test_bit(PG_mte_tagged, &from->flags)) { set_bit(PG_mte_tagged, &to->flags); - page_kasan_tag_reset(to); - /* - * 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_copy_page_tags(kto, kfrom); } } diff --git a/arch/arm64/mm/mteswap.c b/arch/arm64/mm/mteswap.c index a9e50e930484..4334dec93bd4 100644 --- a/arch/arm64/mm/mteswap.c +++ b/arch/arm64/mm/mteswap.c @@ -53,15 +53,6 @@ bool mte_restore_tags(swp_entry_t entry, struct page *page) if (!tags) return false; - 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_restore_page_tags(page_address(page), tags); return true; |