linux-kernel - Re: [PATCH] mm/huge_memory: Fix to make vma_adjust_trans_huge() use find

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Message-ID: <26b82074-891f-4e26-b0a7-328ee2fa08d3@redhat.com>
Date: Thu, 21 Nov 2024 14:44:37 +0100
From: David Hildenbrand <david@...hat.com>
To: Jeongjun Park <aha310510@...il.com>, akpm@...ux-foundation.org
Cc: dave@...olabs.net, willy@...radead.org, Liam.Howlett@...cle.com,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] mm/huge_memory: Fix to make vma_adjust_trans_huge() use
 find_vma() correctly

On 21.11.24 13:41, Jeongjun Park wrote:
> vma_adjust_trans_huge() uses find_vma() to get the VMA, but find_vma() uses
> the returned pointer without any verification, even though it may return NULL.
> In this case, NULL pointer dereference may occur, so to prevent this,
> vma_adjust_trans_huge() should be fix to verify the return value of find_vma().
> 
> Cc: <stable@...r.kernel.org>
> Fixes: 685405020b9f ("mm/khugepaged: stop using vma linked list")

If that's an issue, wouldn't it have predated that commit?

struct vm_area_struct *next = vma->vm_next;
unsigned long nstart = next->vm_start;

Would have also assumed that there is a next VMA that can be 
dereferenced, no?

-- 
Cheers,

David / dhildenb