[PATCH] vma: Detect infinite loop in vma tree

["Liam R. Howlett" <Liam.Howlett@oracle.com>]

From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>

There have been no reported infinite loops in the tree, but checking the
detection of an infinite loop during validation is simple enough.  Add
the detection to the validate_mm() function so that error reports are
clear and don't just report stalls.

This does not protect against internal maple tree issues, but it does
detect too many vmas being returned from the tree.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jann Horn <jannh@google.com>
---
 mm/vma.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/vma.c b/mm/vma.c
index 68138e8c153e..60ed8cc187ad 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -615,7 +615,8 @@ void validate_mm(struct mm_struct *mm)
 			anon_vma_unlock_read(anon_vma);
 		}
 #endif
-		i++;
+		if (++i > mm->map_count)
+			break;
 	}
 	if (i != mm->map_count) {
 		pr_emerg("map_count %d vma iterator %d\n", mm->map_count, i);
-- 
2.43.0