Re: [PATCH 2/2] ovl: fix reference counting in ovl_mmap error path

[Daniel Vetter]

On Wed, Apr 21, 2021 at 03:20:12PM +0200, Christian König wrote:
> mmap_region() now calls fput() on the vma->vm_file.
> 
> Fix this by using vma_set_file() so it doesn't need to be
> handled manually here any more.
> 
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
> Fixes: 1527f926fd04 ("mm: mmap: fix fput in error path v2")
> CC: stable@xxxxxxxxxxxxxxx # 5.11+
> ---
>  fs/overlayfs/file.c | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
> index dbfb35fb0ff7..3847cdc069b5 100644
> --- a/fs/overlayfs/file.c
> +++ b/fs/overlayfs/file.c
> @@ -430,20 +430,11 @@ static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
>  	if (WARN_ON(file != vma->vm_file))
>  		return -EIO;
>  
> -	vma->vm_file = get_file(realfile);
> +	vma_set_file(vma, realfile);

Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>

>  
>  	old_cred = ovl_override_creds(file_inode(file)->i_sb);
>  	ret = call_mmap(vma->vm_file, vma);
>  	revert_creds(old_cred);
> -
> -	if (ret) {
> -		/* Drop reference count from new vm_file value */
> -		fput(realfile);
> -	} else {
> -		/* Drop reference count from previous vm_file value */
> -		fput(file);
> -	}
> -
>  	ovl_file_accessed(file);
>  
>  	return ret;
> -- 
> 2.25.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch