Re: [syzbot] [xfs?] [mm?] WARNING: bad unlock balance in __mm_populate

[Edward Adam Davis]

#syz test

diff --git a/mm/gup.c b/mm/gup.c
index 3883b307780e..4caa7c635320 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1998,7 +1998,11 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
 	struct vm_area_struct *vma = NULL;
 	int locked = 0;
 	long ret = 0;
+	static char poping = 0;
 
+	if (poping)
+		return 0;
+	poping = 1;
 	end = start + len;
 
 	for (nstart = start; nstart < end; nstart = nend) {
@@ -2042,6 +2046,7 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
 	}
 	if (locked)
 		mmap_read_unlock(mm);
+	poping = 0;
 	return ret;	/* 0 or negative error code */
 }
 #else /* CONFIG_MMU */