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From: Suren Baghdasaryan <surenb@google•com>
To: akpm@linux-foundation•org
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Subject: [PATCH v2 4/6] mm: replace vma->vm_flags indirect modification in ksm_madvise
Date: Wed, 25 Jan 2023 00:38:49 -0800	[thread overview]
Message-ID: <20230125083851.27759-5-surenb@google.com> (raw)
In-Reply-To: <20230125083851.27759-1-surenb@google.com>

Replace indirect modifications to vma->vm_flags with calls to modifier
functions to be able to track flag changes and to keep vma locking
correctness. Add a BUG_ON check in ksm_madvise() to catch indirect
vm_flags modification attempts.

Signed-off-by: Suren Baghdasaryan <surenb@google•com>
---
 arch/powerpc/kvm/book3s_hv_uvmem.c | 5 ++++-
 arch/s390/mm/gmap.c                | 5 ++++-
 mm/khugepaged.c                    | 2 ++
 mm/ksm.c                           | 2 ++
 4 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c
index 1d67baa5557a..325a7a47d348 100644
--- a/arch/powerpc/kvm/book3s_hv_uvmem.c
+++ b/arch/powerpc/kvm/book3s_hv_uvmem.c
@@ -393,6 +393,7 @@ static int kvmppc_memslot_page_merge(struct kvm *kvm,
 {
 	unsigned long gfn = memslot->base_gfn;
 	unsigned long end, start = gfn_to_hva(kvm, gfn);
+	unsigned long vm_flags;
 	int ret = 0;
 	struct vm_area_struct *vma;
 	int merge_flag = (merge) ? MADV_MERGEABLE : MADV_UNMERGEABLE;
@@ -409,12 +410,14 @@ static int kvmppc_memslot_page_merge(struct kvm *kvm,
 			ret = H_STATE;
 			break;
 		}
+		vm_flags = vma->vm_flags;
 		ret = ksm_madvise(vma, vma->vm_start, vma->vm_end,
-			  merge_flag, &vma->vm_flags);
+			  merge_flag, &vm_flags);
 		if (ret) {
 			ret = H_STATE;
 			break;
 		}
+		reset_vm_flags(vma, vm_flags);
 		start = vma->vm_end;
 	} while (end > vma->vm_end);
 
diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
index 3a695b8a1e3c..d5eb47dcdacb 100644
--- a/arch/s390/mm/gmap.c
+++ b/arch/s390/mm/gmap.c
@@ -2587,14 +2587,17 @@ int gmap_mark_unmergeable(void)
 {
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
+	unsigned long vm_flags;
 	int ret;
 	VMA_ITERATOR(vmi, mm, 0);
 
 	for_each_vma(vmi, vma) {
+		vm_flags = vma->vm_flags;
 		ret = ksm_madvise(vma, vma->vm_start, vma->vm_end,
-				  MADV_UNMERGEABLE, &vma->vm_flags);
+				  MADV_UNMERGEABLE, &vm_flags);
 		if (ret)
 			return ret;
+		reset_vm_flags(vma, vm_flags);
 	}
 	mm->def_flags &= ~VM_MERGEABLE;
 	return 0;
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 8abc59345bf2..76b24cd0c179 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -354,6 +354,8 @@ struct attribute_group khugepaged_attr_group = {
 int hugepage_madvise(struct vm_area_struct *vma,
 		     unsigned long *vm_flags, int advice)
 {
+	/* vma->vm_flags can be changed only using modifier functions */
+	BUG_ON(vm_flags == &vma->vm_flags);
 	switch (advice) {
 	case MADV_HUGEPAGE:
 #ifdef CONFIG_S390
diff --git a/mm/ksm.c b/mm/ksm.c
index 04f1c8c2df11..992b2be9f5e6 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2573,6 +2573,8 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 	struct mm_struct *mm = vma->vm_mm;
 	int err;
 
+	/* vma->vm_flags can be changed only using modifier functions */
+	BUG_ON(vm_flags == &vma->vm_flags);
 	switch (advice) {
 	case MADV_MERGEABLE:
 		/*
-- 
2.39.1


  parent reply	other threads:[~2023-01-25 11:54 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-25  8:38 [PATCH v2 0/6] introduce vm_flags modifier functions Suren Baghdasaryan
2023-01-25  8:38 ` [PATCH v2 1/6] mm: introduce vma->vm_flags " Suren Baghdasaryan
2023-01-25  8:56   ` Michal Hocko
2023-01-25  9:09   ` Peter Zijlstra
2023-01-25 16:49     ` Suren Baghdasaryan
2023-01-25 18:37       ` Matthew Wilcox
2023-01-25 19:21         ` Suren Baghdasaryan
2023-01-25 18:33   ` Matthew Wilcox
2023-01-25 19:22     ` Suren Baghdasaryan
2023-01-26  9:17   ` Mike Rapoport
2023-01-26 14:50     ` Mike Rapoport
2023-01-26 15:09       ` Matthew Wilcox
2023-01-26 16:25         ` Suren Baghdasaryan
2023-01-25  8:38 ` [PATCH v2 2/6] mm: replace VM_LOCKED_CLEAR_MASK with VM_LOCKED_MASK Suren Baghdasaryan
2023-01-25  9:02   ` Michal Hocko
2023-01-26  9:19   ` Mike Rapoport
2023-01-25  8:38 ` [PATCH v2 3/6] mm: replace vma->vm_flags direct modifications with modifier calls Suren Baghdasaryan
2023-01-25  9:30   ` Michal Hocko
2023-01-25 16:55     ` Suren Baghdasaryan
2023-01-26  9:21   ` Mike Rapoport
2023-01-26 17:07   ` Sebastian Reichel
2023-01-25  8:38 ` Suren Baghdasaryan [this message]
2023-01-25  9:38   ` [PATCH v2 4/6] mm: replace vma->vm_flags indirect modification in ksm_madvise Michal Hocko
2023-01-25 16:57     ` Suren Baghdasaryan
2023-01-25 17:08       ` Michal Hocko
2023-01-25 17:22         ` Suren Baghdasaryan
2023-01-26  9:26   ` Mike Rapoport
2023-01-25  8:38 ` [PATCH v2 5/6] mm: introduce mod_vm_flags_nolock and use it in untrack_pfn Suren Baghdasaryan
2023-01-25  9:42   ` Michal Hocko
2023-01-25 17:00     ` Suren Baghdasaryan
2023-01-26  9:34   ` Mike Rapoport
2023-01-25  8:38 ` [PATCH v2 6/6] mm: export dump_mm() Suren Baghdasaryan
2023-01-25  9:43   ` Michal Hocko
2023-01-26 14:48   ` Mike Rapoport

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