Message-ID: <CADvbK_cFMce0NJjm8VNktjtaTzmiyBX83f0khFqfvdQYn9JphQ@mail.gmail.com>
Date:   Thu, 24 Nov 2022 10:37:22 -0500
From:   Xin Long <lucien.xin@...il.com>
To:     Zhengchao Shao <shaozhengchao@...wei.com>
Cc:     linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
        vyasevich@...il.com, nhorman@...driver.com,
        marcelo.leitner@...il.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        syzkaller-bugs@...glegroups.com, weiyongjun1@...wei.com,
        yuehaibing@...wei.com
Subject: Re: [PATCH net v2] sctp: fix memory leak in sctp_stream_outq_migrate()

On Thu, Nov 24, 2022 at 8:22 AM Zhengchao Shao <shaozhengchao@...wei.com> wrote:
>
> When sctp_stream_outq_migrate() is called to release stream out resources,
> the memory pointed to by prio_head in stream out is not released.
>
> The memory leak information is as follows:
>  unreferenced object 0xffff88801fe79f80 (size 64):
>    comm "sctp_repo", pid 7957, jiffies 4294951704 (age 36.480s)
>    hex dump (first 32 bytes):
>      80 9f e7 1f 80 88 ff ff 80 9f e7 1f 80 88 ff ff  ................
>      90 9f e7 1f 80 88 ff ff 90 9f e7 1f 80 88 ff ff  ................
>    backtrace:
>      [<ffffffff81b215c6>] kmalloc_trace+0x26/0x60
>      [<ffffffff88ae517c>] sctp_sched_prio_set+0x4cc/0x770
>      [<ffffffff88ad64f2>] sctp_stream_init_ext+0xd2/0x1b0
>      [<ffffffff88aa2604>] sctp_sendmsg_to_asoc+0x1614/0x1a30
>      [<ffffffff88ab7ff1>] sctp_sendmsg+0xda1/0x1ef0
>      [<ffffffff87f765ed>] inet_sendmsg+0x9d/0xe0
>      [<ffffffff8754b5b3>] sock_sendmsg+0xd3/0x120
>      [<ffffffff8755446a>] __sys_sendto+0x23a/0x340
>      [<ffffffff87554651>] __x64_sys_sendto+0xe1/0x1b0
>      [<ffffffff89978b49>] do_syscall_64+0x39/0xb0
>      [<ffffffff89a0008b>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> Link: https://syzkaller.appspot.com/bug?exrid=29c402e56c4760763cc0
> Fixes: Fixes: 637784ade221 ("sctp: introduce priority based stream scheduler")
> Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>
> ---
> v2: add .free_sid hook function and use it to free a stream
> ---
>  include/net/sctp/stream_sched.h |  2 ++
>  net/sctp/stream.c               | 15 +++++++++++----
>  net/sctp/stream_sched_prio.c    | 20 ++++++++++++++++++++
>  3 files changed, 33 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/sctp/stream_sched.h b/include/net/sctp/stream_sched.h
> index 01a70b27e026..65058faea4db 100644
> --- a/include/net/sctp/stream_sched.h
> +++ b/include/net/sctp/stream_sched.h
> @@ -26,6 +26,8 @@ struct sctp_sched_ops {
>         int (*init)(struct sctp_stream *stream);
>         /* Init a stream */
>         int (*init_sid)(struct sctp_stream *stream, __u16 sid, gfp_t gfp);
> +       /* free a stream */
> +       void (*free_sid)(struct sctp_stream *stream, __u16 sid);
>         /* Frees the entire thing */
>         void (*free)(struct sctp_stream *stream);
>
> diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> index ef9fceadef8d..0a704bbf1155 100644
> --- a/net/sctp/stream.c
> +++ b/net/sctp/stream.c
> @@ -52,6 +52,15 @@ static void sctp_stream_shrink_out(struct sctp_stream *stream, __u16 outcnt)
>         }
>  }
>
> +static void sctp_stream_free_ext(struct sctp_stream *stream, __u16 sid)
> +{
> +       struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
> +
> +       sched->free_sid(stream, sid);
> +       kfree(SCTP_SO(stream, sid)->ext);
> +       SCTP_SO(stream, sid)->ext = NULL;
> +}
> +
>  /* Migrates chunks from stream queues to new stream queues if needed,
>   * but not across associations. Also, removes those chunks to streams
>   * higher than the new max.
> @@ -76,10 +85,8 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
>                 }
>         }
>
> -       for (i = outcnt; i < stream->outcnt; i++) {
> -               kfree(SCTP_SO(stream, i)->ext);
> -               SCTP_SO(stream, i)->ext = NULL;
> -       }
> +       for (i = outcnt; i < stream->outcnt; i++)
> +               sctp_stream_free_ext(stream, i);
>  }
>
>  static int sctp_stream_alloc_out(struct sctp_stream *stream, __u16 outcnt,
> diff --git a/net/sctp/stream_sched_prio.c b/net/sctp/stream_sched_prio.c
> index 80b5a2c4cbc7..e9cc71b93e90 100644
> --- a/net/sctp/stream_sched_prio.c
> +++ b/net/sctp/stream_sched_prio.c
> @@ -204,6 +204,25 @@ static int sctp_sched_prio_init_sid(struct sctp_stream *stream, __u16 sid,
>         return sctp_sched_prio_set(stream, sid, 0, gfp);
>  }
>
> +static void sctp_sched_prio_free_sid(struct sctp_stream *stream, __u16 sid)
> +{
> +       struct sctp_stream_priorities *prio;
> +       int i;
> +
> +       if (!SCTP_SO(stream, sid)->ext || !SCTP_SO(stream, sid)->ext->prio_head)
> +               return;
It will be better to move "!SCTP_SO(stream, sid)->ext" check to
sctp_stream_free_ext().

> +
> +       prio = SCTP_SO(stream, sid)->ext->prio_head;
> +       SCTP_SO(stream, sid)->ext->prio_head = NULL;
> +       for (i = 0; i < stream->outcnt; i++) {
> +               if (SCTP_SO(stream, i)->ext &&
> +                   SCTP_SO(stream, i)->ext->prio_head == prio)
> +                       return;
> +       }
> +
> +       kfree(prio);
> +}
> +
>  static void sctp_sched_prio_free(struct sctp_stream *stream)
>  {
>         struct sctp_stream_priorities *prio, *n;
> @@ -323,6 +342,7 @@ static struct sctp_sched_ops sctp_sched_prio = {
>         .get = sctp_sched_prio_get,
>         .init = sctp_sched_prio_init,
>         .init_sid = sctp_sched_prio_init_sid,
> +       .free_sid = sctp_sched_prio_free_sid,
Please also add .free_sid for sctp_sched_fcfs/rr,
although they could be empty functions.

Thanks.

>         .free = sctp_sched_prio_free,
>         .enqueue = sctp_sched_prio_enqueue,
>         .dequeue = sctp_sched_prio_dequeue,
> --
> 2.17.1
>

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