linux-kernel - [PATCH] mm: hugetlb: Only prep and add allocated folios for non-gigantic pages

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Message-Id: <20231009145605.2150897-1-usama.arif@bytedance.com>
Date:   Mon,  9 Oct 2023 15:56:05 +0100
From:   Usama Arif <usama.arif@...edance.com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        muchun.song@...ux.dev, mike.kravetz@...cle.com,
        songmuchun@...edance.com, fam.zheng@...edance.com,
        liangma@...ngbit.com, punit.agrawal@...edance.com,
        Usama Arif <usama.arif@...edance.com>
Subject: [PATCH] mm: hugetlb: Only prep and add allocated folios for non-gigantic pages

Calling prep_and_add_allocated_folios when allocating gigantic pages
at boot time causes the kernel to crash as folio_list is empty
and iterating it causes a NULL pointer dereference. Call this only
for non-gigantic pages when folio_list has entires.

Fixes: bfb41d6b2fe148 ("hugetlb: restructure pool allocations")
Signed-off-by: Usama Arif <usama.arif@...edance.com>
---
 mm/hugetlb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index f3749fc125d4..b12f5fd295bb 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3397,7 +3397,8 @@ static void __init hugetlb_hstate_alloc_pages(struct hstate *h)
 	}
 
 	/* list will be empty if hstate_is_gigantic */
-	prep_and_add_allocated_folios(h, &folio_list);
+	if (!hstate_is_gigantic(h))
+		prep_and_add_allocated_folios(h, &folio_list);
 
 	if (i < h->max_huge_pages) {
 		char buf[32];
-- 
2.25.1