This reverts commit add4bc9281e8704e5ab15616b429576c84f453a2.
On Mon, Sep 12, 2022 at 10:52:45AM +0100, Catalin Marinas wrote:
I missed this (holidays) and it looks like it's in stable already. On its own it will likely break kasan_hw if used together with user-space MTE as this change relies on two previous commits:
70c248aca9e7 ("mm: kasan: Skip unpoisoning of user pages") 6d05141a3930 ("mm: kasan: Skip page unpoisoning only if __GFP_SKIP_KASAN_UNPOISON")
The reason I did not cc stable is that there are other dependencies in this area. The potential issues without the above commits were rather theoretical, so take these patches rather as clean-ups/refactoring than fixes.
Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/kernel/hibernate.c | 5 +++++ arch/arm64/kernel/mte.c | 9 +++++++++ arch/arm64/mm/copypage.c | 9 +++++++++ arch/arm64/mm/mteswap.c | 9 +++++++++ 4 files changed, 32 insertions(+)
diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c index af5df48ba915b..2e248342476ea 100644 --- a/arch/arm64/kernel/hibernate.c +++ b/arch/arm64/kernel/hibernate.c @@ -300,6 +300,11 @@ static void swsusp_mte_restore_tags(void) unsigned long pfn = xa_state.xa_index; struct page *page = pfn_to_online_page(pfn);
+ /* + * It is not required to invoke page_kasan_tag_reset(page) + * at this point since the tags stored in page->flags are + * already restored. + */ mte_restore_page_tags(page_address(page), tags);
mte_free_tag_storage(tags); diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index b2b730233274b..f6b00743c3994 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -48,6 +48,15 @@ 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)); }
diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c index 24913271e898c..0dea80bf6de46 100644 --- a/arch/arm64/mm/copypage.c +++ b/arch/arm64/mm/copypage.c @@ -23,6 +23,15 @@ 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 4334dec93bd44..a9e50e930484a 100644 --- a/arch/arm64/mm/mteswap.c +++ b/arch/arm64/mm/mteswap.c @@ -53,6 +53,15 @@ 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;