[PATCH v10 1/6] arm64: mte: Sync tags for pages where PTE is untagged
From: Steven Price <steven.price@arm.com>
Date: 2021-03-12 15:20:09
Also in:
kvmarm, lkml, qemu-devel
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
A KVM guest could store tags in a page even if the VMM hasn't mapped the page with PROT_MTE. So when restoring pages from swap we will need to check to see if there are any saved tags even if !pte_tagged(). However don't check pages which are !pte_valid_user() as these will not have been swapped out. Signed-off-by: Steven Price <steven.price@arm.com> --- arch/arm64/include/asm/pgtable.h | 2 +- arch/arm64/kernel/mte.c | 16 ++++++++++++---- 2 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index e17b96d0e4b5..84166625c989 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h@@ -312,7 +312,7 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr, __sync_icache_dcache(pte); if (system_supports_mte() && - pte_present(pte) && pte_tagged(pte) && !pte_special(pte)) + pte_present(pte) && pte_valid_user(pte) && !pte_special(pte)) mte_sync_tags(ptep, pte); __check_racy_pte_update(mm, ptep, pte);
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index b3c70a612c7a..e016ab57ea36 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c@@ -26,17 +26,23 @@ u64 gcr_kernel_excl __ro_after_init; static bool report_fault_once = true; -static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap) +static void mte_sync_page_tags(struct page *page, pte_t *ptep, bool check_swap, + bool pte_is_tagged) { pte_t old_pte = READ_ONCE(*ptep); if (check_swap && is_swap_pte(old_pte)) { swp_entry_t entry = pte_to_swp_entry(old_pte); - if (!non_swap_entry(entry) && mte_restore_tags(entry, page)) + if (!non_swap_entry(entry) && mte_restore_tags(entry, page)) { + set_bit(PG_mte_tagged, &page->flags); return; + } } + if (!pte_is_tagged || test_and_set_bit(PG_mte_tagged, &page->flags)) + return; + page_kasan_tag_reset(page); /* * We need smp_wmb() in between setting the flags and clearing the
@@ -54,11 +60,13 @@ void mte_sync_tags(pte_t *ptep, pte_t pte) struct page *page = pte_page(pte); long i, nr_pages = compound_nr(page); bool check_swap = nr_pages == 1; + bool pte_is_tagged = pte_tagged(pte); /* if PG_mte_tagged is set, tags have already been initialised */ for (i = 0; i < nr_pages; i++, page++) { - if (!test_and_set_bit(PG_mte_tagged, &page->flags)) - mte_sync_page_tags(page, ptep, check_swap); + if (!test_bit(PG_mte_tagged, &page->flags)) + mte_sync_page_tags(page, ptep, check_swap, + pte_is_tagged); } }
--
2.20.1
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