Subject: [RFC PATCH RESEND 07/28] kernel/fork: mark VMAs as locked before copying pages during fork

From: Suren Baghdasaryan <[email-masked]>
Date: Thu, 1 Sep 2022 10:34:55 -0700

Protect VMAs from concurrent page fault handler while performing
copy_page_range for VMAs having VM_WIPEONFORK flag set.

Signed-off-by: Suren Baghdasaryan <[email-masked]>
---
 kernel/fork.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index bfab31ecd11e..1872ad549fed 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -709,8 +709,10 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 		rb_parent = &tmp->vm_rb;
 
 		mm->map_count++;
-		if (!(tmp->vm_flags & VM_WIPEONFORK))
+		if (!(tmp->vm_flags & VM_WIPEONFORK)) {
+			vma_mark_locked(mpnt);
 			retval = copy_page_range(tmp, mpnt);
+		}
 
 		if (tmp->vm_ops && tmp->vm_ops->open)
 			tmp->vm_ops->open(tmp);
-- 
2.37.2.789.g6183377224-goog