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Date:   Fri, 9 Oct 2020 12:14:18 -0300
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     Christian =?utf-8?B?S8O2bmln?= <ckoenig.leichtzumerken@gmail.com>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org,
        linux-media@vger.kernel.org, chris@chris-wilson.co.uk,
        airlied@redhat.com, akpm@linux-foundation.org, daniel@ffwll.ch,
        sumit.semwal@linaro.org, willy@infradead.org, jhubbard@nvidia.com
Subject: Re: [PATCH 2/6] mm: introduce vma_set_file function v3
Message-ID: <20201009151418.GW5177@ziepe.ca>
References: <20201009150342.1979-1-christian.koenig@amd.com>
 <20201009150342.1979-2-christian.koenig@amd.com>
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In-Reply-To: <20201009150342.1979-2-christian.koenig@amd.com>
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On Fri, Oct 09, 2020 at 05:03:38PM +0200, Christian König wrote:
> +/*
> + * Change backing file, only valid to use during initial VMA setup.
> + */
> +void vma_set_file(struct vm_area_struct *vma, struct file *file)
> +{
> +	if (file)
> +	        get_file(file);
> +
> +	swap(vma->vm_file, file);
> +
> +	if (file)
> +		fput(file);
> +}

fput crashes when file is NULL so the error handling after
unmap_and_free_vma: can't handle this case, similarly vm_file can't be
NULL either.

So just simply:

 swap(vma->vm_file, file);
 get_file(vma->vm_file);
 fput(file);
 
Will do?

Just let it crash if any of them are wrongly NULL.

Jason