Re: [PATCH v5 net] sctp: Free cookie before we memdup a new one

[Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>]

On Thu, Jun 13, 2019 at 06:35:59AM -0400, Neil Horman wrote:
> 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.
> 
> To ensure that we don't leak cookie memory, free any previously
> allocated cookie first.
> 
> Change notes
> v1->v2
> update subsystem tag in subject (davem)
> repeat kfree check for peer_random and peer_hmacs (xin)
> 
> v2->v3
> net->sctp
> also free peer_chunks
> 
> v3->v4
> fix subject tags
> 
> v4->v5
> remove cut line
> 
> Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> Reported-by: syzbot+f7e9153b037eac9b1df8@syzkaller.appspotmail.com
> CC: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
> CC: Xin Long <lucien.xin@gmail.com>
> CC: "David S. Miller" <davem@davemloft.net>
> CC: netdev@vger.kernel.org

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

> ---
>  net/sctp/sm_make_chunk.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
> index f17908f5c4f3..9b0e5b0d701a 100644
> --- a/net/sctp/sm_make_chunk.c
> +++ b/net/sctp/sm_make_chunk.c
> @@ -2583,6 +2583,8 @@ static int sctp_process_param(struct sctp_association *asoc,
>  	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;
> @@ -2647,6 +2649,8 @@ static int sctp_process_param(struct sctp_association *asoc,
>  			goto fall_through;
>  
>  		/* Save peer's random parameter */
> +		if (asoc->peer.peer_random)
> +			kfree(asoc->peer.peer_random);
>  		asoc->peer.peer_random = kmemdup(param.p,
>  					    ntohs(param.p->length), gfp);
>  		if (!asoc->peer.peer_random) {
> @@ -2660,6 +2664,8 @@ static int sctp_process_param(struct sctp_association *asoc,
>  			goto fall_through;
>  
>  		/* Save peer's HMAC list */
> +		if (asoc->peer.peer_hmacs)
> +			kfree(asoc->peer.peer_hmacs);
>  		asoc->peer.peer_hmacs = kmemdup(param.p,
>  					    ntohs(param.p->length), gfp);
>  		if (!asoc->peer.peer_hmacs) {
> @@ -2675,6 +2681,8 @@ static int sctp_process_param(struct sctp_association *asoc,
>  		if (!ep->auth_enable)
>  			goto fall_through;
>  
> +		if (asoc->peer.peer_chunks)
> +			kfree(asoc->peer.peer_chunks);
>  		asoc->peer.peer_chunks = kmemdup(param.p,
>  					    ntohs(param.p->length), gfp);
>  		if (!asoc->peer.peer_chunks)
> -- 
> 2.20.1
>