linux-kernel - Re: [PATCH] ppp: deflate: Fix possible crash in deflate

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Date:   Tue, 14 May 2019 16:05:48 +0200
From:   Guillaume Nault <gnault@...hat.com>
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     davem@...emloft.net, paulus@...ba.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] ppp: deflate: Fix possible crash in deflate_init

On Tue, May 14, 2019 at 03:43:00PM +0800, YueHaibing wrote:
> 
> If ppp_deflate fails to register in deflate_init,
> module initialization failed out, however
> ppp_deflate_draft may has been regiestred and not
> unregistered before return.
> Then the seconed modprobe will trigger crash like this.
> 
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>  drivers/net/ppp/ppp_deflate.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ppp/ppp_deflate.c b/drivers/net/ppp/ppp_deflate.c
> index b5edc7f..2829efe 100644
> --- a/drivers/net/ppp/ppp_deflate.c
> +++ b/drivers/net/ppp/ppp_deflate.c
> @@ -610,12 +610,16 @@ static void z_incomp(void *arg, unsigned char *ibuf, int icnt)
>  
>  static int __init deflate_init(void)
>  {
> -        int answer = ppp_register_compressor(&ppp_deflate);
> -        if (answer == 0)
> -                printk(KERN_INFO
> -		       "PPP Deflate Compression module registered\n");
> +	int answer;
> +
> +	answer = ppp_register_compressor(&ppp_deflate);
> +	if (answer)
> +		return answer;
> +
> +	pr_info("PPP Deflate Compression module registered\n");
>  	ppp_register_compressor(&ppp_deflate_draft);
> -        return answer;
> +
> +	return 0;
>  }
>  
I'd be cleaner to also check for ppp_deflate_draft registration failure
IMHO (and print the log line only if both compressors get registered
successfully).