linux-kernel - [PATCH] mm: vmalloc: BUG_ON if mapping size is not PAGE

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Message-Id: <20251009035943.526-1-yadong.qi@linux.alibaba.com>
Date: Thu,  9 Oct 2025 11:59:43 +0800
From: Yadong Qi <yadong.qi@...ux.alibaba.com>
To: akpm@...ux-foundation.org,
	urezki@...il.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	ying.huang@...ux.alibaba.com
Cc: Yadong Qi <yadong.qi@...ux.alibaba.com>
Subject: [PATCH] mm: vmalloc: BUG_ON if mapping size is not PAGE_SIZE aligned

In mm/vmalloc.c, the function vmap_pte_range() assumes that the
mapping size is aligned to PAGE_SIZE. If this assumption is
violated, the loop will become infinite because the termination
condition (`addr != end`) will never be met. This can lead to
overwriting other VA ranges and/or random pages physically follow
the page table.

It's the caller's responsibility to ensure that the mapping size
is aligned to PAGE_SIZE. However, the memory corruption is hard
to root cause. To identify the programming error in the caller
easier, check whether the mapping size is PAGE_SIZE aligned with
BUG_ON().

Signed-off-by: Yadong Qi <yadong.qi@...ux.alibaba.com>
Reviewed-by: Huang Ying <ying.huang@...ux.alibaba.com>
---
 mm/vmalloc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 5edd536ba9d2..b54d3ee6b202 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -100,6 +100,8 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 	struct page *page;
 	unsigned long size = PAGE_SIZE;

+	BUG_ON(!PAGE_ALIGNED(end - addr));
+
 	pfn = phys_addr >> PAGE_SHIFT;
 	pte = pte_alloc_kernel_track(pmd, addr, mask);
 	if (!pte)
-- 
2.43.5