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Date:   Thu, 20 May 2021 20:47:19 -0700
From:   Davidlohr Bueso <dave@stgolabs.net>
To:     Liam Howlett <liam.howlett@oracle.com>
Cc:     "maple-tree@lists.infradead.org" <maple-tree@lists.infradead.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Song Liu <songliubraving@fb.com>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        Laurent Dufour <ldufour@linux.ibm.com>,
        David Rientjes <rientjes@google.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Rik van Riel <riel@surriel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Michel Lespinasse <michel@lespinasse.org>
Subject: Re: [PATCH 20/22] mm/mremap: Use vma_lookup() in vma_to_resize()
Message-ID: <20210521034719.fkaotqikwisie4kq@offworld>
Mail-Followup-To: Liam Howlett <liam.howlett@oracle.com>,
        "maple-tree@lists.infradead.org" <maple-tree@lists.infradead.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Song Liu <songliubraving@fb.com>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        Matthew Wilcox <willy@infradead.org>,
        Laurent Dufour <ldufour@linux.ibm.com>,
        David Rientjes <rientjes@google.com>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Vlastimil Babka <vbabka@suse.cz>, Rik van Riel <riel@surriel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Michel Lespinasse <michel@lespinasse.org>
References: <20210510165839.2692974-1-Liam.Howlett@Oracle.com>
 <20210510165839.2692974-21-Liam.Howlett@Oracle.com>
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On Mon, 10 May 2021, Liam Howlett wrote:

>Use vma_lookup() to find the VMA at a specific address.  As vma_lookup()
>will return NULL if the address is not within any VMA, the start address
>no longer needs to be validated.
>
>Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
>---
> mm/mremap.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/mm/mremap.c b/mm/mremap.c
>index 47c255b60150..04143755cd1e 100644
>--- a/mm/mremap.c
>+++ b/mm/mremap.c
>@@ -634,10 +634,10 @@ static struct vm_area_struct *vma_to_resize(unsigned long addr,
> 	unsigned long *p)
> {
> 	struct mm_struct *mm = current->mm;
>-	struct vm_area_struct *vma = find_vma(mm, addr);
>+	struct vm_area_struct *vma = vma_lookup(mm, addr);
> 	unsigned long pgoff;
>

Nit, but could the vma_lookup() call be separate from the declaration
of vma?

	vma = find_vma();
>-	if (!vma || vma->vm_start > addr)
>+	if (!vma)
> 		return ERR_PTR(-EFAULT);

Thanks,
Davidlohr