From 332c11344a3c5b064982d556dd40c7a17fdf44e9 Mon Sep 17 00:00:00 2001
From: Suraj Sonawane <surajsonawane0215@gmail.com>
Date: Mon, 25 Nov 2024 13:19:48 +0530
Subject: [PATCH] v2fix kernel BUG in const_folio_flags

syz test

Signed-off-by: Suraj Sonawane <surajsonawane0215@gmail.com>
---
 include/linux/page-flags.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 2220bfec2..214ad9d6d 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -8,6 +8,7 @@
 
 #include <linux/types.h>
 #include <linux/bug.h>
+#include <linux/mm.h>
 #include <linux/mmdebug.h>
 #ifndef __GENERATING_BOUNDS_H
 #include <linux/mm_types.h>
@@ -306,6 +307,12 @@ static const unsigned long *const_folio_flags(const struct folio *folio,
 {
 	const struct page *page = &folio->page;
 
+	long nr_pages = folio_nr_pages(folio);
+	if (n >= nr_pages) {
+		pr_err("Invalid folio index: n=%u, folio_nr_pages=%u\n", n, folio_nr_pages(folio));
+		return -EINVAL;
+	}
+
 	VM_BUG_ON_PGFLAGS(PageTail(page), page);
 	VM_BUG_ON_PGFLAGS(n > 0 && !test_bit(PG_head, &page->flags), page);
 	return &page[n].flags;
-- 
2.34.1