linux-kernel - Re: [PATCH] ovl: Fix potential memory leak

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Date:   Mon, 22 Aug 2022 15:57:34 +0200
From:   David Disseldorp <ddiss@...e.de>
To:     Stanislav Goriainov <goriainov@...ras.ru>
Cc:     Miklos Szeredi <miklos@...redi.hu>, linux-unionfs@...r.kernel.org,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org
Subject: Re: [PATCH] ovl: Fix potential memory leak

On Mon, 22 Aug 2022 14:52:57 +0300, Stanislav Goriainov wrote:

> ovl: Fix potential memory leak in ovl_lookup()
> 
> If memory for uperredirect was allocated with kstrdup()
> in upperdir != NULL and d.redirect != NULL path,
> it may be lost when upperredirect is reassigned later.
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Stanislav Goriainov <goriainov@...ras.ru>
> ---
>  fs/overlayfs/namei.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
> index 69dc577974f8..226c69812379 100644
> --- a/fs/overlayfs/namei.c
> +++ b/fs/overlayfs/namei.c
> @@ -1085,6 +1085,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
>  			.mnt = ovl_upper_mnt(ofs),
>  		};
>  
> +		kfree(upperredirect);
>  		upperredirect = ovl_get_redirect_xattr(ofs, &upperpath, 0);
>  		if (IS_ERR(upperredirect)) {
>  			err = PTR_ERR(upperredirect);

This probably deserves a:
Fixes: 0a2d0d3f2f291 ("ovl: Check redirect on index as well")

Looks fine otherwise.
Reviewed-by: David Disseldorp <ddiss@...e.de>