From: Catalin Marinas catalin.marinas@arm.com
[ Upstream commit 20794545c14692094a882d2221c251c4573e6adf ]
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 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 deletions(-)
diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c index 6328308be272..7754ef328657 100644 --- a/arch/arm64/kernel/hibernate.c +++ b/arch/arm64/kernel/hibernate.c @@ -300,11 +300,6 @@ 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 d502703e8373..d565ae25e48f 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -47,15 +47,6 @@ 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)); }
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;