[merged mm-hotfixes-stable] fs-proc-task_mmu-move-mmu-notification-mechanism-inside-mm-lock.patch removed from -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

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The quilt patch titled
     Subject: fs/proc/task_mmu: move mmu notification mechanism inside mm lock
has been removed from the -mm tree.  Its filename was
     fs-proc-task_mmu-move-mmu-notification-mechanism-inside-mm-lock.patch

This patch was dropped because it was merged into the mm-hotfixes-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Muhammad Usama Anjum <usama.anjum@collabora.com>
Subject: fs/proc/task_mmu: move mmu notification mechanism inside mm lock
Date: Tue, 9 Jan 2024 16:24:42 +0500

Move mmu notification mechanism inside mm lock to prevent race condition
in other components which depend on it.  The notifier will invalidate
memory range.  Depending upon the number of iterations, different memory
ranges would be invalidated.

The following warning would be removed by this patch:
WARNING: CPU: 0 PID: 5067 at arch/x86/kvm/../../../virt/kvm/kvm_main.c:734 kvm_mmu_notifier_change_pte+0x860/0x960 arch/x86/kvm/../../../virt/kvm/kvm_main.c:734

There is no behavioural and performance change with this patch when
there is no component registered with the mmu notifier.

[akpm@linux-foundation.org: narrow the scope of `range', per Sean]
Link: https://lkml.kernel.org/r/20240109112445.590736-1-usama.anjum@collabora.com
Fixes: 52526ca7fdb9 ("fs/proc/task_mmu: implement IOCTL to get and optionally clear info about PTEs")
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Reported-by: syzbot+81227d2bd69e9dedb802@syzkaller.appspotmail.com
Link: https://lore.kernel.org/all/000000000000f6d051060c6785bc@google.com/
Reviewed-by: Sean Christopherson <seanjc@google.com>
Cc: Andrei Vagin <avagin@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/proc/task_mmu.c |   24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

--- a/fs/proc/task_mmu.c~fs-proc-task_mmu-move-mmu-notification-mechanism-inside-mm-lock
+++ a/fs/proc/task_mmu.c
@@ -2432,7 +2432,6 @@ static long pagemap_scan_flush_buffer(st
 
 static long do_pagemap_scan(struct mm_struct *mm, unsigned long uarg)
 {
-	struct mmu_notifier_range range;
 	struct pagemap_scan_private p = {0};
 	unsigned long walk_start;
 	size_t n_ranges_out = 0;
@@ -2448,15 +2447,9 @@ static long do_pagemap_scan(struct mm_st
 	if (ret)
 		return ret;
 
-	/* Protection change for the range is going to happen. */
-	if (p.arg.flags & PM_SCAN_WP_MATCHING) {
-		mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,
-					mm, p.arg.start, p.arg.end);
-		mmu_notifier_invalidate_range_start(&range);
-	}
-
 	for (walk_start = p.arg.start; walk_start < p.arg.end;
 			walk_start = p.arg.walk_end) {
+		struct mmu_notifier_range range;
 		long n_out;
 
 		if (fatal_signal_pending(current)) {
@@ -2467,8 +2460,20 @@ static long do_pagemap_scan(struct mm_st
 		ret = mmap_read_lock_killable(mm);
 		if (ret)
 			break;
+
+		/* Protection change for the range is going to happen. */
+		if (p.arg.flags & PM_SCAN_WP_MATCHING) {
+			mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_VMA, 0,
+						mm, walk_start, p.arg.end);
+			mmu_notifier_invalidate_range_start(&range);
+		}
+
 		ret = walk_page_range(mm, walk_start, p.arg.end,
 				      &pagemap_scan_ops, &p);
+
+		if (p.arg.flags & PM_SCAN_WP_MATCHING)
+			mmu_notifier_invalidate_range_end(&range);
+
 		mmap_read_unlock(mm);
 
 		n_out = pagemap_scan_flush_buffer(&p);
@@ -2494,9 +2499,6 @@ static long do_pagemap_scan(struct mm_st
 	if (pagemap_scan_writeback_args(&p.arg, uarg))
 		ret = -EFAULT;
 
-	if (p.arg.flags & PM_SCAN_WP_MATCHING)
-		mmu_notifier_invalidate_range_end(&range);
-
 	kfree(p.vec_buf);
 	return ret;
 }
_

Patches currently in -mm which might be from usama.anjum@collabora.com are

selftests-mm-mremap_test-fix-build-warning.patch
selftests-mm-hugepage-shm-conform-test-to-tap-format-output.patch
selftests-mm-hugepage-vmemmap-conform-test-to-tap-format-output.patch
selftests-mm-hugetlb-madvise-conform-test-to-tap-format-output.patch
selftests-mm-khugepaged-conform-test-to-tap-format-output.patch
selftests-mm-hugetlb-read-hwpoison-conform-test-to-tap-format-output.patch
selftests-mm-ksm_tests-conform-test-to-tap-format-output.patch
selftests-mm-config-add-missing-configs.patch