Commit ce919583 authored by David Hildenbrand's avatar David Hildenbrand Committed by Kefeng Wang
Browse files

mm/memory: handle !page case in zap_present_pte() separately 

mainline inclusion
from mainline-v6.9-rc1
commit 0cf18e839f64fff9a58569cc9a596bf97310e044
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I9CHB4
CVE: NA

-------------------------------------------------

We don't need uptodate accessed/dirty bits, so in theory we could replace
ptep_get_and_clear_full() by an optimized ptep_clear_full() function.
Let's rely on the provided pte.

Further, there is no scenario where we would have to insert uffd-wp
markers when zapping something that is not a normal page (i.e., zeropage).
Add a sanity check to make sure this remains true.

should_zap_folio() no longer has to handle NULL pointers.  This change
replaces 2/3 "!page/!folio" checks by a single "!page" one.

Note that arch_check_zapped_pte() on x86-64 checks the HW-dirty bit to
detect shadow stack entries.  But for shadow stack entries, the HW dirty
bit (in combination with non-writable PTEs) is set by software.  So for
the arch_check_zapped_pte() check, we don't have to sync against HW
setting the HW dirty bit concurrently, it is always set.

Link: https://lkml.kernel.org/r/20240214204435.167852-3-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarRyan Roberts <ryan.roberts@arm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 0cf18e839f64fff9a58569cc9a596bf97310e044)
Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
parent b5be205e

mm/memory.c

+11 −11
Original line number Diff line number Diff line
@@ -1500,10 +1500,6 @@ static inline bool should_zap_folio(struct zap_details *details, 
	if (should_zap_cows(details))

		return true;



	/* E.g. the caller passes NULL for the case of a zero folio */

	if (!folio)

		return true;



	/* Otherwise we should only zap non-anon folios */

	return !folio_test_anon(folio);

}
@@ -1541,24 +1537,28 @@ static inline void zap_present_pte(struct mmu_gather *tlb, 
		int *rss, bool *force_flush, bool *force_break)

{

	struct mm_struct *mm = tlb->mm;

	struct folio *folio = NULL;

	bool delay_rmap = false;

	struct folio *folio;

	struct page *page;



	page = vm_normal_page(vma, addr, ptent);

	if (page)

		folio = page_folio(page);

	if (!page) {

		/* We don't need up-to-date accessed/dirty bits. */

		ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);

		arch_check_zapped_pte(vma, ptent);

		tlb_remove_tlb_entry(tlb, pte, addr);

		VM_WARN_ON_ONCE(userfaultfd_wp(vma));

		ksm_might_unmap_zero_page(mm, ptent);

		return;

	}



	folio = page_folio(page);

	if (unlikely(!should_zap_folio(details, folio)))

		return;

	ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm);

	arch_check_zapped_pte(vma, ptent);

	tlb_remove_tlb_entry(tlb, pte, addr);

	zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent);

	if (unlikely(!page)) {

		ksm_might_unmap_zero_page(mm, ptent);

		return;

	}



	if (!folio_test_anon(folio)) {

		if (pte_dirty(ptent)) {