linux-kernel - Re: [PATCH v2] consolemap: Fix a memory leaking bug in drivers/tty/vt/consolemap.c

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Message-ID: <201905230952.B47ADA17A@keescook>
Date:   Thu, 23 May 2019 09:54:18 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Gen Zhang <blackgod016574@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     jslaby@...e.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] consolemap: Fix a memory leaking bug in
 drivers/tty/vt/consolemap.c

On Thu, May 23, 2019 at 08:34:52AM +0800, Gen Zhang wrote:
> In function con_insert_unipair(), when allocation for p2 and p1[n]
> fails, ENOMEM is returned, but previously allocated p1 is not freed, 
> remains as leaking memory. Thus we should free p1 as well when this
> allocation fails.
> 
> Signed-off-by: Gen Zhang <blackgod016574@...il.com>

As far as I can see this is correct, as it's just restoring the prior
state before the p1 allocation.

Reviewed-by: Kees Cook <keescook@...omium.org>

> ---
> diff --git a/drivers/tty/vt/consolemap.c b/drivers/tty/vt/consolemap.c
> index b28aa0d..79fcc96 100644
> --- a/drivers/tty/vt/consolemap.c
> +++ b/drivers/tty/vt/consolemap.c
> @@ -489,7 +489,11 @@ con_insert_unipair(struct uni_pagedir *p, u_short unicode, u_short fontpos)
>  	p2 = p1[n = (unicode >> 6) & 0x1f];
>  	if (!p2) {
>  		p2 = p1[n] = kmalloc_array(64, sizeof(u16), GFP_KERNEL);
> -		if (!p2) return -ENOMEM;
> +		if (!p2) {
> +			kfree(p1);
> +			p->uni_pgdir[n] = NULL;
> +			return -ENOMEM;
> +		}
>  		memset(p2, 0xff, 64*sizeof(u16)); /* No glyphs for the characters (yet) */
>  	}
>  
> ---

-- 
Kees Cook