netdev - Re: [PATCH v4 net] sctp: Free cookie before we memdup a new one

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Date:   Thu, 13 Jun 2019 01:58:59 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     Neil Horman <nhorman@...driver.com>
Cc:     linux-sctp@...r.kernel.org, network dev <netdev@...r.kernel.org>,
        syzbot+f7e9153b037eac9b1df8@...kaller.appspotmail.com,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH v4 net] sctp: Free cookie before we memdup a new one

On Wed, Jun 12, 2019 at 8:38 AM Neil Horman <nhorman@...driver.com> 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
>
> Signed-off-by: Neil Horman <nhorman@...driver.com>
> Reported-by: syzbot+f7e9153b037eac9b1df8@...kaller.appspotmail.com
> CC: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
> CC: Xin Long <lucien.xin@...il.com>
> CC: "David S. Miller" <davem@...emloft.net>
> CC: netdev@...r.kernel.org
> ---
>  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
>
Reviewed-by: Xin Long <lucien.xin@...il.com>