linux-kernel - Re: [PATCH 4.19 10/61] sctp: Free cookie before we memdup a new one

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Message-ID: <20190622082011.GB10751@amd>
Date:   Sat, 22 Jun 2019 10:20:11 +0200
From:   Pavel Machek <pavel@...x.de>
To:     pavel@....cz
Cc:     linux-kernel@...r.kernel.org, Neil Horman <nhorman@...driver.com>,
        syzbot+f7e9153b037eac9b1df8@...kaller.appspotmail.com,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Xin Long <lucien.xin@...il.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 4.19 10/61] sctp: Free cookie before we memdup a new one

Hi!

On Thu 2019-06-20 19:57:05, Greg Kroah-Hartman wrote:
> From: Neil Horman <nhorman@...driver.com>
> 
> [ Upstream commit ce950f1050cece5e406a5cde723c69bba60e1b26 ]
> 
> Based on comments from Xin, even after fixes for our recent syzbot
> report of cookie memory leaks, its possible to get a resend of an INIT
> chunk which would lead to us leaking cookie memory.
> 

> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -2600,6 +2600,8 @@ do_addr_param:
>  	case SCTP_PARAM_STATE_COOKIE:
>  		asoc->peer.cookie_len =
>  			ntohs(param.p->length) - sizeof(struct sctp_paramhdr);
> +		if (asoc->peer.cookie)
> +			kfree(asoc->peer.cookie);
>  		asoc->peer.cookie = kmemdup(param.cookie->body, asoc->peer.cookie_len, gfp);
>  		if (!asoc->peer.cookie)
>  			retval = 0;

kfree() handles NULL just fine. Can we simply work without the tests
and save a bit of code?

										Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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