[RFC PATCH 06/28] mm: mark VMA as locked whenever vma->vm_flags are modified

[Suren Baghdasaryan]

VMA flag modifications should be done under VMA lock to prevent concurrent
page fault handling in that area.

Signed-off-by: Suren Baghdasaryan <surenb at google.com>
---
 fs/proc/task_mmu.c | 1 +
 fs/userfaultfd.c   | 6 ++++++
 mm/madvise.c       | 1 +
 mm/mlock.c         | 2 ++
 mm/mmap.c          | 1 +
 mm/mprotect.c      | 1 +
 6 files changed, 12 insertions(+)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 4e0023643f8b..ceffa5c2c650 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1285,6 +1285,7 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
 			for (vma = mm->mmap; vma; vma = vma->vm_next) {
 				if (!(vma->vm_flags & VM_SOFTDIRTY))
 					continue;
+				vma_mark_locked(vma);
 				vma->vm_flags &= ~VM_SOFTDIRTY;
 				vma_set_page_prot(vma);
 			}
diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index 175de70e3adf..fe557b3d1c07 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -620,6 +620,7 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
 		mmap_write_lock(mm);
 		for (vma = mm->mmap; vma; vma = vma->vm_next)
 			if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) {
+				vma_mark_locked(vma);
 				vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
 				vma->vm_flags &= ~__VM_UFFD_FLAGS;
 			}
@@ -653,6 +654,7 @@ int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
 
 	octx = vma->vm_userfaultfd_ctx.ctx;
 	if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) {
+		vma_mark_locked(vma);
 		vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
 		vma->vm_flags &= ~__VM_UFFD_FLAGS;
 		return 0;
@@ -734,6 +736,7 @@ void mremap_userfaultfd_prep(struct vm_area_struct *vma,
 		atomic_inc(&ctx->mmap_changing);
 	} else {
 		/* Drop uffd context if remap feature not enabled */
+		vma_mark_locked(vma);
 		vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
 		vma->vm_flags &= ~__VM_UFFD_FLAGS;
 	}
@@ -891,6 +894,7 @@ static int userfaultfd_release(struct inode *inode, struct file *file)
 			vma = prev;
 		else
 			prev = vma;
+		vma_mark_locked(vma);
 		vma->vm_flags = new_flags;
 		vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
 	}
@@ -1449,6 +1453,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
 		 * the next vma was merged into the current one and
 		 * the current one has not been updated yet.
 		 */
+		vma_mark_locked(vma);
 		vma->vm_flags = new_flags;
 		vma->vm_userfaultfd_ctx.ctx = ctx;
 
@@ -1630,6 +1635,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
 		 * the next vma was merged into the current one and
 		 * the current one has not been updated yet.
 		 */
+		vma_mark_locked(vma);
 		vma->vm_flags = new_flags;
 		vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
 
diff --git a/mm/madvise.c b/mm/madvise.c
index 5f0f0948a50e..a173f0025abd 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -181,6 +181,7 @@ static int madvise_update_vma(struct vm_area_struct *vma,
 	/*
 	 * vm_flags is protected by the mmap_lock held in write mode.
 	 */
+	vma_mark_locked(vma);
 	vma->vm_flags = new_flags;
 	if (!vma->vm_file) {
 		error = replace_anon_vma_name(vma, anon_name);
diff --git a/mm/mlock.c b/mm/mlock.c
index b14e929084cc..f62e1a4d05f2 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -380,6 +380,7 @@ static void mlock_vma_pages_range(struct vm_area_struct *vma,
 	 */
 	if (newflags & VM_LOCKED)
 		newflags |= VM_IO;
+	vma_mark_locked(vma);
 	WRITE_ONCE(vma->vm_flags, newflags);
 
 	lru_add_drain();
@@ -456,6 +457,7 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
 
 	if ((newflags & VM_LOCKED) && (oldflags & VM_LOCKED)) {
 		/* No work to do, and mlocking twice would be wrong */
+		vma_mark_locked(vma);
 		vma->vm_flags = newflags;
 	} else {
 		mlock_vma_pages_range(vma, start, end, newflags);
diff --git a/mm/mmap.c b/mm/mmap.c
index 693e6776be39..f89c9b058105 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1818,6 +1818,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 out:
 	perf_event_mmap(vma);
 
+	vma_mark_locked(vma);
 	vm_stat_account(mm, vm_flags, len >> PAGE_SHIFT);
 	if (vm_flags & VM_LOCKED) {
 		if ((vm_flags & VM_SPECIAL) || vma_is_dax(vma) ||
diff --git a/mm/mprotect.c b/mm/mprotect.c
index bc6bddd156ca..df47fc21b0e4 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -621,6 +621,7 @@ mprotect_fixup(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	 * vm_flags and vm_page_prot are protected by the mmap_lock
 	 * held in write mode.
 	 */
+	vma_mark_locked(vma);
 	vma->vm_flags = newflags;
 	/*
 	 * We want to check manually if we can change individual PTEs writable
-- 
2.37.2.672.g94769d06f0-goog