linux-kernel - Re: [PATCH] udf: prevent memory leak in udf_new

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Message-ID: <20190925222408.GN26530@ZenIV.linux.org.uk>
Date:   Wed, 25 Sep 2019 23:24:08 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Navid Emamdoost <navid.emamdoost@...il.com>
Cc:     emamd001@....edu, kjlu@....edu, smccaman@....edu,
        Jan Kara <jack@...e.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] udf: prevent memory leak in udf_new_inode

On Wed, Sep 25, 2019 at 04:39:03PM -0500, Navid Emamdoost wrote:
> In udf_new_inode if either udf_new_block or insert_inode_locked fials
> the allocated memory for iinfo->i_ext.i_data should be released.

"... because of such-and-such reasons" part appears to be missing.
Why should it be released there?

> Signed-off-by: Navid Emamdoost <navid.emamdoost@...il.com>
> ---
>  fs/udf/ialloc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/udf/ialloc.c b/fs/udf/ialloc.c
> index 0adb40718a5d..b8ab3acab6b6 100644
> --- a/fs/udf/ialloc.c
> +++ b/fs/udf/ialloc.c
> @@ -86,6 +86,7 @@ struct inode *udf_new_inode(struct inode *dir, umode_t mode)
>  			      dinfo->i_location.partitionReferenceNum,
>  			      start, &err);
>  	if (err) {
> +		kfree(iinfo->i_ext.i_data);
>  		iput(inode);
>  		return ERR_PTR(err);
>  	}

Have you tested that?  Because it has all earmarks of double-free;
normal eviction pathway ought to free the damn thing.  <greps around
a bit>

Mind explaining what's to stop ->evict_inode (== udf_evict_inode) from
hitting
        kfree(iinfo->i_ext.i_data);
considering that this call of kfree() appears to be unconditional there?

> @@ -130,6 +131,7 @@ struct inode *udf_new_inode(struct inode *dir, umode_t mode)
>  	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
>  	iinfo->i_crtime = inode->i_mtime;
>  	if (unlikely(insert_inode_locked(inode) < 0)) {
> +		kfree(iinfo->i_ext.i_data);
>  		make_bad_inode(inode);
>  		iput(inode);
>  		return ERR_PTR(-EIO);

And the same here.