[PATCH net] sctp: fix memory leak in sctp_stream_outq_migrate()

[PATCH net] sctp: fix memory leak in sctp_stream_outq_migrate()

[Zhengchao Shao]

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

Fixes: 637784ade221 ("sctp: introduce priority based stream scheduler")
Reported-by: syzbot+29c402e56c4760763cc0@syzkaller.appspotmail.com
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
---
 net/sctp/stream.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/sctp/stream.c b/net/sctp/stream.c
index ef9fceadef8d..a17dc368876f 100644
--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -70,6 +70,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
 		 * sctp_stream_update will swap ->out pointers.
 		 */
 		for (i = 0; i < outcnt; i++) {
+			if (SCTP_SO(new, i)->ext)
+				kfree(SCTP_SO(new, i)->ext->prio_head);
+
 			kfree(SCTP_SO(new, i)->ext);
 			SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
 			SCTP_SO(stream, i)->ext = NULL;
@@ -77,6 +80,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
 	}
 
 	for (i = outcnt; i < stream->outcnt; i++) {
+		if (SCTP_SO(stream, i)->ext)
+			kfree(SCTP_SO(stream, i)->ext->prio_head);
+
 		kfree(SCTP_SO(stream, i)->ext);
 		SCTP_SO(stream, i)->ext = NULL;
 	}
-- 
2.17.1

Re: [PATCH net] sctp: fix memory leak in sctp_stream_outq_migrate()

[Xin Long]

On Fri, Nov 18, 2022 at 3:48 AM Zhengchao Shao <shaozhengchao@huawei.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
>
> Fixes: 637784ade221 ("sctp: introduce priority based stream scheduler")
> Reported-by: syzbot+29c402e56c4760763cc0@syzkaller.appspotmail.com
> Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> ---
>  net/sctp/stream.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> index ef9fceadef8d..a17dc368876f 100644
> --- a/net/sctp/stream.c
> +++ b/net/sctp/stream.c
> @@ -70,6 +70,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
>                  * sctp_stream_update will swap ->out pointers.
>                  */
>                 for (i = 0; i < outcnt; i++) {
> +                       if (SCTP_SO(new, i)->ext)
> +                               kfree(SCTP_SO(new, i)->ext->prio_head);
> +
>                         kfree(SCTP_SO(new, i)->ext);
>                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
>                         SCTP_SO(stream, i)->ext = NULL;
> @@ -77,6 +80,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
>         }
>
>         for (i = outcnt; i < stream->outcnt; i++) {
> +               if (SCTP_SO(stream, i)->ext)
> +                       kfree(SCTP_SO(stream, i)->ext->prio_head);
> +
>                 kfree(SCTP_SO(stream, i)->ext);
>                 SCTP_SO(stream, i)->ext = NULL;
>         }
> --
> 2.17.1
>
This is not a proper fix:
1. you shouldn't access "prio_head" outside stream_sched_prio.c.
2. the prio_head you freed might be used by other out streams, freeing
it unconditionally would cause either a double free or use after free.

I'm afraid we have to add a ".free_sid" in sctp_sched_ops, and
implement it for sctp_sched_prio, like:

+static void sctp_sched_prio_free_sid(struct sctp_stream *stream, __u16 sid)
+{
+       struct sctp_stream_priorities *prio = SCTP_SO(stream,
sid)->ext->prio_head;
+       int i;
+
+       if (!prio)
+               return;
+
+       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 +340,7 @@ 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,
        .free = sctp_sched_prio_free,
        .enqueue = sctp_sched_prio_enqueue,
        .dequeue = sctp_sched_prio_dequeue,

then call it in sctp_stream_outq_migrate(), like:

+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.
@@ -70,16 +79,14 @@ static void sctp_stream_outq_migrate(struct
sctp_stream *stream,
                 * sctp_stream_update will swap ->out pointers.
                 */
                for (i = 0; i < outcnt; i++) {
-                       kfree(SCTP_SO(new, i)->ext);
+                       sctp_stream_free_ext(new, i);
                        SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
                        SCTP_SO(stream, i)->ext = NULL;
                }
        }

-       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(new, i);
 }

Marcelo, do you see a better solution?

Thanks.

Re: [PATCH net] sctp: fix memory leak in sctp_stream_outq_migrate()

[Marcelo Ricardo Leitner]

On Fri, Nov 18, 2022 at 10:15:50PM -0500, Xin Long wrote:
> On Fri, Nov 18, 2022 at 3:48 AM Zhengchao Shao <shaozhengchao@huawei.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
> >
> > Fixes: 637784ade221 ("sctp: introduce priority based stream scheduler")
> > Reported-by: syzbot+29c402e56c4760763cc0@syzkaller.appspotmail.com
> > Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> > ---
> >  net/sctp/stream.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> > index ef9fceadef8d..a17dc368876f 100644
> > --- a/net/sctp/stream.c
> > +++ b/net/sctp/stream.c
> > @@ -70,6 +70,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> >                  * sctp_stream_update will swap ->out pointers.
> >                  */
> >                 for (i = 0; i < outcnt; i++) {
> > +                       if (SCTP_SO(new, i)->ext)
> > +                               kfree(SCTP_SO(new, i)->ext->prio_head);
> > +
> >                         kfree(SCTP_SO(new, i)->ext);
> >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> >                         SCTP_SO(stream, i)->ext = NULL;
> > @@ -77,6 +80,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> >         }
> >
> >         for (i = outcnt; i < stream->outcnt; i++) {
> > +               if (SCTP_SO(stream, i)->ext)
> > +                       kfree(SCTP_SO(stream, i)->ext->prio_head);
> > +
> >                 kfree(SCTP_SO(stream, i)->ext);
> >                 SCTP_SO(stream, i)->ext = NULL;
> >         }
> > --
> > 2.17.1
> >
> This is not a proper fix:
> 1. you shouldn't access "prio_head" outside stream_sched_prio.c.
> 2. the prio_head you freed might be used by other out streams, freeing
> it unconditionally would cause either a double free or use after free.
> 
> I'm afraid we have to add a ".free_sid" in sctp_sched_ops, and
> implement it for sctp_sched_prio, like:
> 
> +static void sctp_sched_prio_free_sid(struct sctp_stream *stream, __u16 sid)
> +{
> +       struct sctp_stream_priorities *prio = SCTP_SO(stream,
> sid)->ext->prio_head;
> +       int i;
> +
> +       if (!prio)
> +               return;
> +
> +       SCTP_SO(stream, sid)->ext->prio_head = NULL;
> +       for (i = 0; i < stream->outcnt; i++) {

Instead of checking all streams, the for() can/should be replaced by
(from sctp_sched_prio_free):
	if (!list_empty(&prio->prio_sched))
		return;

> +               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 +340,7 @@ 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,
>         .free = sctp_sched_prio_free,
>         .enqueue = sctp_sched_prio_enqueue,
>         .dequeue = sctp_sched_prio_dequeue,
> 
> then call it in sctp_stream_outq_migrate(), like:
> 
> +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.
> @@ -70,16 +79,14 @@ static void sctp_stream_outq_migrate(struct
> sctp_stream *stream,
>                  * sctp_stream_update will swap ->out pointers.
>                  */
>                 for (i = 0; i < outcnt; i++) {
> -                       kfree(SCTP_SO(new, i)->ext);
> +                       sctp_stream_free_ext(new, i);
>                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
>                         SCTP_SO(stream, i)->ext = NULL;
>                 }
>         }
> 
> -       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(new, i);
>  }
> 
> Marcelo, do you see a better solution?

No. Your suggestion is the best I could think of too.

Another approach would be to expose sched->free and do all the freeing
at once, like sctp_stream_free() does. But the above is looks cleaner
and makes it evident that freeing 'ext' is not trivial.

With the proposal above, sctp_sched_prio_free() becomes an
optimization, if we can call it that. With the for/if replacement
above, not even that, and should be removed. Including sctp_sched_ops
'free' pointer.

sctp_stream_free() then should be updated to use the new
sctp_stream_free_ext() instead, instead of mangling it directly.

Makes sense?

Thanks,
Marcelo

Re: [PATCH net] sctp: fix memory leak in sctp_stream_outq_migrate()

[Xin Long]

On Tue, Nov 22, 2022 at 6:35 PM Marcelo Ricardo Leitner
<marcelo.leitner@gmail.com> wrote:
>
> On Fri, Nov 18, 2022 at 10:15:50PM -0500, Xin Long wrote:
> > On Fri, Nov 18, 2022 at 3:48 AM Zhengchao Shao <shaozhengchao@huawei.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
> > >
> > > Fixes: 637784ade221 ("sctp: introduce priority based stream scheduler")
> > > Reported-by: syzbot+29c402e56c4760763cc0@syzkaller.appspotmail.com
> > > Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> > > ---
> > >  net/sctp/stream.c | 6 ++++++
> > >  1 file changed, 6 insertions(+)
> > >
> > > diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> > > index ef9fceadef8d..a17dc368876f 100644
> > > --- a/net/sctp/stream.c
> > > +++ b/net/sctp/stream.c
> > > @@ -70,6 +70,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > >                  * sctp_stream_update will swap ->out pointers.
> > >                  */
> > >                 for (i = 0; i < outcnt; i++) {
> > > +                       if (SCTP_SO(new, i)->ext)
> > > +                               kfree(SCTP_SO(new, i)->ext->prio_head);
> > > +
> > >                         kfree(SCTP_SO(new, i)->ext);
> > >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> > >                         SCTP_SO(stream, i)->ext = NULL;
> > > @@ -77,6 +80,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > >         }
> > >
> > >         for (i = outcnt; i < stream->outcnt; i++) {
> > > +               if (SCTP_SO(stream, i)->ext)
> > > +                       kfree(SCTP_SO(stream, i)->ext->prio_head);
> > > +
> > >                 kfree(SCTP_SO(stream, i)->ext);
> > >                 SCTP_SO(stream, i)->ext = NULL;
> > >         }
> > > --
> > > 2.17.1
> > >
> > This is not a proper fix:
> > 1. you shouldn't access "prio_head" outside stream_sched_prio.c.
> > 2. the prio_head you freed might be used by other out streams, freeing
> > it unconditionally would cause either a double free or use after free.
> >
> > I'm afraid we have to add a ".free_sid" in sctp_sched_ops, and
> > implement it for sctp_sched_prio, like:
> >
> > +static void sctp_sched_prio_free_sid(struct sctp_stream *stream, __u16 sid)
> > +{
> > +       struct sctp_stream_priorities *prio = SCTP_SO(stream,
> > sid)->ext->prio_head;
> > +       int i;
> > +
> > +       if (!prio)
> > +               return;
> > +
> > +       SCTP_SO(stream, sid)->ext->prio_head = NULL;
> > +       for (i = 0; i < stream->outcnt; i++) {
>
> Instead of checking all streams, the for() can/should be replaced by
> (from sctp_sched_prio_free):
>         if (!list_empty(&prio->prio_sched))
>                 return;
sctp_stream_outq_migrate() is called after unsched_all() for "stream",
list_empty(prio_sched) is expected to be true.

Note that kfree(SCTP_SO(new, i)->ext) shouldn't have the reported
problem, as at that moment, the "new" stream hasn't been set
stream_sched yet. It means there's only one place that needs to
call free_sid in sctp_stream_outq_migrate().
(Maybe Zhengchao can help us confirm this?)

>
> > +               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 +340,7 @@ 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,
> >         .free = sctp_sched_prio_free,
> >         .enqueue = sctp_sched_prio_enqueue,
> >         .dequeue = sctp_sched_prio_dequeue,
> >
> > then call it in sctp_stream_outq_migrate(), like:
> >
> > +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.
> > @@ -70,16 +79,14 @@ static void sctp_stream_outq_migrate(struct
> > sctp_stream *stream,
> >                  * sctp_stream_update will swap ->out pointers.
> >                  */
> >                 for (i = 0; i < outcnt; i++) {
> > -                       kfree(SCTP_SO(new, i)->ext);
> > +                       sctp_stream_free_ext(new, i);
> >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> >                         SCTP_SO(stream, i)->ext = NULL;
> >                 }
> >         }
> >
> > -       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(new, i);
> >  }
> >
> > Marcelo, do you see a better solution?
>
> No. Your suggestion is the best I could think of too.
>
> Another approach would be to expose sched->free and do all the freeing
> at once, like sctp_stream_free() does. But the above is looks cleaner
> and makes it evident that freeing 'ext' is not trivial.
>
> With the proposal above, sctp_sched_prio_free() becomes an
> optimization, if we can call it that. With the for/if replacement
> above, not even that, and should be removed. Including sctp_sched_ops
> 'free' pointer.
Or we extract the common code to another function, like
sctp_sched_prio_free_head(stream, prio), and pass prio as
NULL in sctp_sched_prio_free() for freeing all.

>
> sctp_stream_free() then should be updated to use the new
> sctp_stream_free_ext() instead, instead of mangling it directly.
I thought about this, but there is ".free", which is more efficient
to free all prio than calling ".free_sid" outcnt times.

I may move free_sid() out of sctp_stream_free_ext(), then in
sctp_stream_free() we can call sctp_stream_free_ext() without
calling free_sid(), or just remove sctp_stream_free_ext().

Thanks.

>
> Makes sense?
>
> Thanks,
> Marcelo

Re: [PATCH net] sctp: fix memory leak in sctp_stream_outq_migrate()

[Marcelo Ricardo Leitner]

On Wed, Nov 23, 2022 at 12:20:44PM -0500, Xin Long wrote:
> On Tue, Nov 22, 2022 at 6:35 PM Marcelo Ricardo Leitner
> <marcelo.leitner@gmail.com> wrote:
> >
> > On Fri, Nov 18, 2022 at 10:15:50PM -0500, Xin Long wrote:
> > > On Fri, Nov 18, 2022 at 3:48 AM Zhengchao Shao <shaozhengchao@huawei.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
> > > >
> > > > Fixes: 637784ade221 ("sctp: introduce priority based stream scheduler")
> > > > Reported-by: syzbot+29c402e56c4760763cc0@syzkaller.appspotmail.com
> > > > Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> > > > ---
> > > >  net/sctp/stream.c | 6 ++++++
> > > >  1 file changed, 6 insertions(+)
> > > >
> > > > diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> > > > index ef9fceadef8d..a17dc368876f 100644
> > > > --- a/net/sctp/stream.c
> > > > +++ b/net/sctp/stream.c
> > > > @@ -70,6 +70,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > > >                  * sctp_stream_update will swap ->out pointers.
> > > >                  */
> > > >                 for (i = 0; i < outcnt; i++) {
> > > > +                       if (SCTP_SO(new, i)->ext)
> > > > +                               kfree(SCTP_SO(new, i)->ext->prio_head);
> > > > +
> > > >                         kfree(SCTP_SO(new, i)->ext);
> > > >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> > > >                         SCTP_SO(stream, i)->ext = NULL;
> > > > @@ -77,6 +80,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > > >         }
> > > >
> > > >         for (i = outcnt; i < stream->outcnt; i++) {
> > > > +               if (SCTP_SO(stream, i)->ext)
> > > > +                       kfree(SCTP_SO(stream, i)->ext->prio_head);
> > > > +
> > > >                 kfree(SCTP_SO(stream, i)->ext);
> > > >                 SCTP_SO(stream, i)->ext = NULL;
> > > >         }
> > > > --
> > > > 2.17.1
> > > >
> > > This is not a proper fix:
> > > 1. you shouldn't access "prio_head" outside stream_sched_prio.c.
> > > 2. the prio_head you freed might be used by other out streams, freeing
> > > it unconditionally would cause either a double free or use after free.
> > >
> > > I'm afraid we have to add a ".free_sid" in sctp_sched_ops, and
> > > implement it for sctp_sched_prio, like:
> > >
> > > +static void sctp_sched_prio_free_sid(struct sctp_stream *stream, __u16 sid)
> > > +{
> > > +       struct sctp_stream_priorities *prio = SCTP_SO(stream,
> > > sid)->ext->prio_head;
> > > +       int i;
> > > +
> > > +       if (!prio)
> > > +               return;
> > > +
> > > +       SCTP_SO(stream, sid)->ext->prio_head = NULL;
> > > +       for (i = 0; i < stream->outcnt; i++) {
> >
> > Instead of checking all streams, the for() can/should be replaced by
> > (from sctp_sched_prio_free):
> >         if (!list_empty(&prio->prio_sched))
> >                 return;
> sctp_stream_outq_migrate() is called after unsched_all() for "stream",
> list_empty(prio_sched) is expected to be true.

Good point. Am I missing something or the 'prio_head == prio' below
would always be false then as well?

Anyhow, as this is moving to something that can potentially be called
from other places afterwards, keeping the check doesn't hurt.

> 
> Note that kfree(SCTP_SO(new, i)->ext) shouldn't have the reported
> problem, as at that moment, the "new" stream hasn't been set
> stream_sched yet. It means there's only one place that needs to
> call free_sid in sctp_stream_outq_migrate().
> (Maybe Zhengchao can help us confirm this?)

That's the case in Tetsuo's patch (earlier today) as well. Yet, if we
have an official way to free a stream, if it's not error handling
during initialization, it should use it.

> 
> >
> > > +               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 +340,7 @@ 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,
> > >         .free = sctp_sched_prio_free,
> > >         .enqueue = sctp_sched_prio_enqueue,
> > >         .dequeue = sctp_sched_prio_dequeue,
> > >
> > > then call it in sctp_stream_outq_migrate(), like:
> > >
> > > +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.
> > > @@ -70,16 +79,14 @@ static void sctp_stream_outq_migrate(struct
> > > sctp_stream *stream,
> > >                  * sctp_stream_update will swap ->out pointers.
> > >                  */
> > >                 for (i = 0; i < outcnt; i++) {
> > > -                       kfree(SCTP_SO(new, i)->ext);
> > > +                       sctp_stream_free_ext(new, i);
> > >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> > >                         SCTP_SO(stream, i)->ext = NULL;
> > >                 }
> > >         }
> > >
> > > -       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(new, i);
> > >  }
> > >
> > > Marcelo, do you see a better solution?
> >
> > No. Your suggestion is the best I could think of too.
> >
> > Another approach would be to expose sched->free and do all the freeing
> > at once, like sctp_stream_free() does. But the above is looks cleaner
> > and makes it evident that freeing 'ext' is not trivial.
> >
> > With the proposal above, sctp_sched_prio_free() becomes an
> > optimization, if we can call it that. With the for/if replacement
> > above, not even that, and should be removed. Including sctp_sched_ops
> > 'free' pointer.
> Or we extract the common code to another function, like
> sctp_sched_prio_free_head(stream, prio), and pass prio as
> NULL in sctp_sched_prio_free() for freeing all.
> 
> >
> > sctp_stream_free() then should be updated to use the new
> > sctp_stream_free_ext() instead, instead of mangling it directly.
> I thought about this, but there is ".free", which is more efficient
> to free all prio than calling ".free_sid" outcnt times.

How much more efficient, just by avoiding retpoline stuff on the
indirect functional call or something else?

> 
> I may move free_sid() out of sctp_stream_free_ext(), then in
> sctp_stream_free() we can call sctp_stream_free_ext() without
> calling free_sid(), or just remove sctp_stream_free_ext().

It's easier to maintain it if we have symmetric paths for initializing
and for freeing it and less special cases. We already have
sctp_stream_init_ext(), so having sctp_stream_free_ext() is not off.

I'm happy to review any patch that also updates sctp_stream_free(),
one way or another.

> 
> Thanks.
> 
> >
> > Makes sense?
> >
> > Thanks,
> > Marcelo

Re: [PATCH net] sctp: fix memory leak in sctp_stream_outq_migrate()

[Xin Long]

(

On Wed, Nov 23, 2022 at 1:10 PM Marcelo Ricardo Leitner
<marcelo.leitner@gmail.com> wrote:
>
> On Wed, Nov 23, 2022 at 12:20:44PM -0500, Xin Long wrote:
> > On Tue, Nov 22, 2022 at 6:35 PM Marcelo Ricardo Leitner
> > <marcelo.leitner@gmail.com> wrote:
> > >
> > > On Fri, Nov 18, 2022 at 10:15:50PM -0500, Xin Long wrote:
> > > > On Fri, Nov 18, 2022 at 3:48 AM Zhengchao Shao <shaozhengchao@huawei.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
> > > > >
> > > > > Fixes: 637784ade221 ("sctp: introduce priority based stream scheduler")
> > > > > Reported-by: syzbot+29c402e56c4760763cc0@syzkaller.appspotmail.com
> > > > > Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> > > > > ---
> > > > >  net/sctp/stream.c | 6 ++++++
> > > > >  1 file changed, 6 insertions(+)
> > > > >
> > > > > diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> > > > > index ef9fceadef8d..a17dc368876f 100644
> > > > > --- a/net/sctp/stream.c
> > > > > +++ b/net/sctp/stream.c
> > > > > @@ -70,6 +70,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > > > >                  * sctp_stream_update will swap ->out pointers.
> > > > >                  */
> > > > >                 for (i = 0; i < outcnt; i++) {
> > > > > +                       if (SCTP_SO(new, i)->ext)
> > > > > +                               kfree(SCTP_SO(new, i)->ext->prio_head);
> > > > > +
> > > > >                         kfree(SCTP_SO(new, i)->ext);
> > > > >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> > > > >                         SCTP_SO(stream, i)->ext = NULL;
> > > > > @@ -77,6 +80,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > > > >         }
> > > > >
> > > > >         for (i = outcnt; i < stream->outcnt; i++) {
> > > > > +               if (SCTP_SO(stream, i)->ext)
> > > > > +                       kfree(SCTP_SO(stream, i)->ext->prio_head);
> > > > > +
> > > > >                 kfree(SCTP_SO(stream, i)->ext);
> > > > >                 SCTP_SO(stream, i)->ext = NULL;
> > > > >         }
> > > > > --
> > > > > 2.17.1
> > > > >
> > > > This is not a proper fix:
> > > > 1. you shouldn't access "prio_head" outside stream_sched_prio.c.
> > > > 2. the prio_head you freed might be used by other out streams, freeing
> > > > it unconditionally would cause either a double free or use after free.
> > > >
> > > > I'm afraid we have to add a ".free_sid" in sctp_sched_ops, and
> > > > implement it for sctp_sched_prio, like:
> > > >
> > > > +static void sctp_sched_prio_free_sid(struct sctp_stream *stream, __u16 sid)
> > > > +{
> > > > +       struct sctp_stream_priorities *prio = SCTP_SO(stream,
> > > > sid)->ext->prio_head;
> > > > +       int i;
> > > > +
> > > > +       if (!prio)
> > > > +               return;
> > > > +
> > > > +       SCTP_SO(stream, sid)->ext->prio_head = NULL;
> > > > +       for (i = 0; i < stream->outcnt; i++) {
> > >
> > > Instead of checking all streams, the for() can/should be replaced by
> > > (from sctp_sched_prio_free):
> > >         if (!list_empty(&prio->prio_sched))
> > >                 return;
> > sctp_stream_outq_migrate() is called after unsched_all() for "stream",
> > list_empty(prio_sched) is expected to be true.
>
> Good point. Am I missing something or the 'prio_head == prio' below
> would always be false then as well?
>
> Anyhow, as this is moving to something that can potentially be called
> from other places afterwards, keeping the check doesn't hurt.
>
> >
> > Note that kfree(SCTP_SO(new, i)->ext) shouldn't have the reported
> > problem, as at that moment, the "new" stream hasn't been set
> > stream_sched yet. It means there's only one place that needs to
> > call free_sid in sctp_stream_outq_migrate().
> > (Maybe Zhengchao can help us confirm this?)
>
> That's the case in Tetsuo's patch (earlier today) as well. Yet, if we
> have an official way to free a stream, if it's not error handling
> during initialization, it should use it.
right.

>
> >
> > >
> > > > +               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 +340,7 @@ 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,
> > > >         .free = sctp_sched_prio_free,
> > > >         .enqueue = sctp_sched_prio_enqueue,
> > > >         .dequeue = sctp_sched_prio_dequeue,
> > > >
> > > > then call it in sctp_stream_outq_migrate(), like:
> > > >
> > > > +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.
> > > > @@ -70,16 +79,14 @@ static void sctp_stream_outq_migrate(struct
> > > > sctp_stream *stream,
> > > >                  * sctp_stream_update will swap ->out pointers.
> > > >                  */
> > > >                 for (i = 0; i < outcnt; i++) {
> > > > -                       kfree(SCTP_SO(new, i)->ext);
> > > > +                       sctp_stream_free_ext(new, i);
> > > >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> > > >                         SCTP_SO(stream, i)->ext = NULL;
> > > >                 }
> > > >         }
> > > >
> > > > -       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(new, i);
> > > >  }
> > > >
> > > > Marcelo, do you see a better solution?
> > >
> > > No. Your suggestion is the best I could think of too.
> > >
> > > Another approach would be to expose sched->free and do all the freeing
> > > at once, like sctp_stream_free() does. But the above is looks cleaner
> > > and makes it evident that freeing 'ext' is not trivial.
> > >
> > > With the proposal above, sctp_sched_prio_free() becomes an
> > > optimization, if we can call it that. With the for/if replacement
> > > above, not even that, and should be removed. Including sctp_sched_ops
> > > 'free' pointer.
> > Or we extract the common code to another function, like
> > sctp_sched_prio_free_head(stream, prio), and pass prio as
> > NULL in sctp_sched_prio_free() for freeing all.
> >
> > >
> > > sctp_stream_free() then should be updated to use the new
> > > sctp_stream_free_ext() instead, instead of mangling it directly.
> > I thought about this, but there is ".free", which is more efficient
> > to free all prio than calling ".free_sid" outcnt times.
>
> How much more efficient, just by avoiding retpoline stuff on the
> indirect functional call or something else?

in sctp_stream_free():
.free() will be called one time to free all prios
while .free_sid will be called in a loop to  free all prios:
        for (i = 0; i < stream->outcnt; i++)
               .free_sid(stream, i);

inside either() .free or . free_sid() there is another loop:
for (i = 0; i < stream->outcnt; i++)
    ...

That's why I said using .free() in sctp_stream_free() will be more efficient.

>
> >
> > I may move free_sid() out of sctp_stream_free_ext(), then in
> > sctp_stream_free() we can call sctp_stream_free_ext() without
> > calling free_sid(), or just remove sctp_stream_free_ext().
>
> It's easier to maintain it if we have symmetric paths for initializing
> and for freeing it and less special cases. We already have
> sctp_stream_init_ext(), so having sctp_stream_free_ext() is not off.
didn't notice init_sid in sctp_stream_init_ext(), it makes sense to
have free_sid in sctp_stream_free_ext().

Thanks.

>
> I'm happy to review any patch that also updates sctp_stream_free(),
> one way or another.
>
> >
> > Thanks.
> >
> > >
> > > Makes sense?
> > >
> > > Thanks,
> > > Marcelo

Re: [PATCH net] sctp: fix memory leak in sctp_stream_outq_migrate()

[Xin Long]

On Wed, Nov 23, 2022 at 1:30 PM Xin Long <lucien.xin@gmail.com> wrote:
>
> (
>
> On Wed, Nov 23, 2022 at 1:10 PM Marcelo Ricardo Leitner
> <marcelo.leitner@gmail.com> wrote:
> >
> > On Wed, Nov 23, 2022 at 12:20:44PM -0500, Xin Long wrote:
> > > On Tue, Nov 22, 2022 at 6:35 PM Marcelo Ricardo Leitner
> > > <marcelo.leitner@gmail.com> wrote:
> > > >
> > > > On Fri, Nov 18, 2022 at 10:15:50PM -0500, Xin Long wrote:
> > > > > On Fri, Nov 18, 2022 at 3:48 AM Zhengchao Shao <shaozhengchao@huawei.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
> > > > > >
> > > > > > Fixes: 637784ade221 ("sctp: introduce priority based stream scheduler")
> > > > > > Reported-by: syzbot+29c402e56c4760763cc0@syzkaller.appspotmail.com
> > > > > > Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> > > > > > ---
> > > > > >  net/sctp/stream.c | 6 ++++++
> > > > > >  1 file changed, 6 insertions(+)
> > > > > >
> > > > > > diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> > > > > > index ef9fceadef8d..a17dc368876f 100644
> > > > > > --- a/net/sctp/stream.c
> > > > > > +++ b/net/sctp/stream.c
> > > > > > @@ -70,6 +70,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > > > > >                  * sctp_stream_update will swap ->out pointers.
> > > > > >                  */
> > > > > >                 for (i = 0; i < outcnt; i++) {
> > > > > > +                       if (SCTP_SO(new, i)->ext)
> > > > > > +                               kfree(SCTP_SO(new, i)->ext->prio_head);
> > > > > > +
> > > > > >                         kfree(SCTP_SO(new, i)->ext);
> > > > > >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> > > > > >                         SCTP_SO(stream, i)->ext = NULL;
> > > > > > @@ -77,6 +80,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > > > > >         }
> > > > > >
> > > > > >         for (i = outcnt; i < stream->outcnt; i++) {
> > > > > > +               if (SCTP_SO(stream, i)->ext)
> > > > > > +                       kfree(SCTP_SO(stream, i)->ext->prio_head);
> > > > > > +
> > > > > >                 kfree(SCTP_SO(stream, i)->ext);
> > > > > >                 SCTP_SO(stream, i)->ext = NULL;
> > > > > >         }
> > > > > > --
> > > > > > 2.17.1
> > > > > >
> > > > > This is not a proper fix:
> > > > > 1. you shouldn't access "prio_head" outside stream_sched_prio.c.
> > > > > 2. the prio_head you freed might be used by other out streams, freeing
> > > > > it unconditionally would cause either a double free or use after free.
> > > > >
> > > > > I'm afraid we have to add a ".free_sid" in sctp_sched_ops, and
> > > > > implement it for sctp_sched_prio, like:
> > > > >
> > > > > +static void sctp_sched_prio_free_sid(struct sctp_stream *stream, __u16 sid)
> > > > > +{
> > > > > +       struct sctp_stream_priorities *prio = SCTP_SO(stream,
> > > > > sid)->ext->prio_head;
> > > > > +       int i;
> > > > > +
> > > > > +       if (!prio)
> > > > > +               return;
> > > > > +
> > > > > +       SCTP_SO(stream, sid)->ext->prio_head = NULL;
> > > > > +       for (i = 0; i < stream->outcnt; i++) {
> > > >
> > > > Instead of checking all streams, the for() can/should be replaced by
> > > > (from sctp_sched_prio_free):
> > > >         if (!list_empty(&prio->prio_sched))
> > > >                 return;
> > > sctp_stream_outq_migrate() is called after unsched_all() for "stream",
> > > list_empty(prio_sched) is expected to be true.
> >
> > Good point. Am I missing something or the 'prio_head == prio' below
> > would always be false then as well?
sorry, forgot to reply to this one :D

after .unsched_all, multiple outstreams may have the same prio_head,
which are not on any list (like stream->prio_list).

so when freeing one outstream ext, it will need to go over all outstreams' exts
and check if this outstream ext's prio is equal to that of any other outstreams.

> >
> > Anyhow, as this is moving to something that can potentially be called
> > from other places afterwards, keeping the check doesn't hurt.
> >
> > >
> > > Note that kfree(SCTP_SO(new, i)->ext) shouldn't have the reported
> > > problem, as at that moment, the "new" stream hasn't been set
> > > stream_sched yet. It means there's only one place that needs to
> > > call free_sid in sctp_stream_outq_migrate().
> > > (Maybe Zhengchao can help us confirm this?)
> >
> > That's the case in Tetsuo's patch (earlier today) as well. Yet, if we
> > have an official way to free a stream, if it's not error handling
> > during initialization, it should use it.
> right.
>
> >
> > >
> > > >
> > > > > +               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 +340,7 @@ 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,
> > > > >         .free = sctp_sched_prio_free,
> > > > >         .enqueue = sctp_sched_prio_enqueue,
> > > > >         .dequeue = sctp_sched_prio_dequeue,
> > > > >
> > > > > then call it in sctp_stream_outq_migrate(), like:
> > > > >
> > > > > +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.
> > > > > @@ -70,16 +79,14 @@ static void sctp_stream_outq_migrate(struct
> > > > > sctp_stream *stream,
> > > > >                  * sctp_stream_update will swap ->out pointers.
> > > > >                  */
> > > > >                 for (i = 0; i < outcnt; i++) {
> > > > > -                       kfree(SCTP_SO(new, i)->ext);
> > > > > +                       sctp_stream_free_ext(new, i);
> > > > >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> > > > >                         SCTP_SO(stream, i)->ext = NULL;
> > > > >                 }
> > > > >         }
> > > > >
> > > > > -       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(new, i);
> > > > >  }
> > > > >
> > > > > Marcelo, do you see a better solution?
> > > >
> > > > No. Your suggestion is the best I could think of too.
> > > >
> > > > Another approach would be to expose sched->free and do all the freeing
> > > > at once, like sctp_stream_free() does. But the above is looks cleaner
> > > > and makes it evident that freeing 'ext' is not trivial.
> > > >
> > > > With the proposal above, sctp_sched_prio_free() becomes an
> > > > optimization, if we can call it that. With the for/if replacement
> > > > above, not even that, and should be removed. Including sctp_sched_ops
> > > > 'free' pointer.
> > > Or we extract the common code to another function, like
> > > sctp_sched_prio_free_head(stream, prio), and pass prio as
> > > NULL in sctp_sched_prio_free() for freeing all.
> > >
> > > >
> > > > sctp_stream_free() then should be updated to use the new
> > > > sctp_stream_free_ext() instead, instead of mangling it directly.
> > > I thought about this, but there is ".free", which is more efficient
> > > to free all prio than calling ".free_sid" outcnt times.
> >
> > How much more efficient, just by avoiding retpoline stuff on the
> > indirect functional call or something else?
>
> in sctp_stream_free():
> .free() will be called one time to free all prios
> while .free_sid will be called in a loop to  free all prios:
>         for (i = 0; i < stream->outcnt; i++)
>                .free_sid(stream, i);
>
> inside either() .free or . free_sid() there is another loop:
> for (i = 0; i < stream->outcnt; i++)
>     ...
>
> That's why I said using .free() in sctp_stream_free() will be more efficient.
>
> >
> > >
> > > I may move free_sid() out of sctp_stream_free_ext(), then in
> > > sctp_stream_free() we can call sctp_stream_free_ext() without
> > > calling free_sid(), or just remove sctp_stream_free_ext().
> >
> > It's easier to maintain it if we have symmetric paths for initializing
> > and for freeing it and less special cases. We already have
> > sctp_stream_init_ext(), so having sctp_stream_free_ext() is not off.
> didn't notice init_sid in sctp_stream_init_ext(), it makes sense to
> have free_sid in sctp_stream_free_ext().
>
> Thanks.
>
> >
> > I'm happy to review any patch that also updates sctp_stream_free(),
> > one way or another.
> >
> > >
> > > Thanks.
> > >
> > > >
> > > > Makes sense?
> > > >
> > > > Thanks,
> > > > Marcelo

Re: [PATCH net] sctp: fix memory leak in sctp_stream_outq_migrate()

[Marcelo Ricardo Leitner]

On Wed, Nov 23, 2022 at 01:48:01PM -0500, Xin Long wrote:
> On Wed, Nov 23, 2022 at 1:30 PM Xin Long <lucien.xin@gmail.com> wrote:
> >
> > (
> >
> > On Wed, Nov 23, 2022 at 1:10 PM Marcelo Ricardo Leitner
> > <marcelo.leitner@gmail.com> wrote:
> > >
> > > On Wed, Nov 23, 2022 at 12:20:44PM -0500, Xin Long wrote:
> > > > On Tue, Nov 22, 2022 at 6:35 PM Marcelo Ricardo Leitner
> > > > <marcelo.leitner@gmail.com> wrote:
> > > > >
> > > > > On Fri, Nov 18, 2022 at 10:15:50PM -0500, Xin Long wrote:
> > > > > > On Fri, Nov 18, 2022 at 3:48 AM Zhengchao Shao <shaozhengchao@huawei.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
> > > > > > >
> > > > > > > Fixes: 637784ade221 ("sctp: introduce priority based stream scheduler")
> > > > > > > Reported-by: syzbot+29c402e56c4760763cc0@syzkaller.appspotmail.com
> > > > > > > Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> > > > > > > ---
> > > > > > >  net/sctp/stream.c | 6 ++++++
> > > > > > >  1 file changed, 6 insertions(+)
> > > > > > >
> > > > > > > diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> > > > > > > index ef9fceadef8d..a17dc368876f 100644
> > > > > > > --- a/net/sctp/stream.c
> > > > > > > +++ b/net/sctp/stream.c
> > > > > > > @@ -70,6 +70,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > > > > > >                  * sctp_stream_update will swap ->out pointers.
> > > > > > >                  */
> > > > > > >                 for (i = 0; i < outcnt; i++) {
> > > > > > > +                       if (SCTP_SO(new, i)->ext)
> > > > > > > +                               kfree(SCTP_SO(new, i)->ext->prio_head);
> > > > > > > +
> > > > > > >                         kfree(SCTP_SO(new, i)->ext);
> > > > > > >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> > > > > > >                         SCTP_SO(stream, i)->ext = NULL;
> > > > > > > @@ -77,6 +80,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > > > > > >         }
> > > > > > >
> > > > > > >         for (i = outcnt; i < stream->outcnt; i++) {
> > > > > > > +               if (SCTP_SO(stream, i)->ext)
> > > > > > > +                       kfree(SCTP_SO(stream, i)->ext->prio_head);
> > > > > > > +
> > > > > > >                 kfree(SCTP_SO(stream, i)->ext);
> > > > > > >                 SCTP_SO(stream, i)->ext = NULL;
> > > > > > >         }
> > > > > > > --
> > > > > > > 2.17.1
> > > > > > >
> > > > > > This is not a proper fix:
> > > > > > 1. you shouldn't access "prio_head" outside stream_sched_prio.c.
> > > > > > 2. the prio_head you freed might be used by other out streams, freeing
> > > > > > it unconditionally would cause either a double free or use after free.
> > > > > >
> > > > > > I'm afraid we have to add a ".free_sid" in sctp_sched_ops, and
> > > > > > implement it for sctp_sched_prio, like:
> > > > > >
> > > > > > +static void sctp_sched_prio_free_sid(struct sctp_stream *stream, __u16 sid)
> > > > > > +{
> > > > > > +       struct sctp_stream_priorities *prio = SCTP_SO(stream,
> > > > > > sid)->ext->prio_head;
> > > > > > +       int i;
> > > > > > +
> > > > > > +       if (!prio)
> > > > > > +               return;
> > > > > > +
> > > > > > +       SCTP_SO(stream, sid)->ext->prio_head = NULL;
> > > > > > +       for (i = 0; i < stream->outcnt; i++) {
> > > > >
> > > > > Instead of checking all streams, the for() can/should be replaced by
> > > > > (from sctp_sched_prio_free):
> > > > >         if (!list_empty(&prio->prio_sched))
> > > > >                 return;
> > > > sctp_stream_outq_migrate() is called after unsched_all() for "stream",
> > > > list_empty(prio_sched) is expected to be true.
> > >
> > > Good point. Am I missing something or the 'prio_head == prio' below
> > > would always be false then as well?
> sorry, forgot to reply to this one :D

:D

> 
> after .unsched_all, multiple outstreams may have the same prio_head,
> which are not on any list (like stream->prio_list).
> 
> so when freeing one outstream ext, it will need to go over all outstreams' exts
> and check if this outstream ext's prio is equal to that of any other outstreams.

Understood. The check in sctp_sched_prio_free() is actually checking
if the prio_head is not yet scheduled for freeing instead, right.
Thanks. Hmm. This for() can be quite expensive then. :-(

> 
> > >
> > > Anyhow, as this is moving to something that can potentially be called
> > > from other places afterwards, keeping the check doesn't hurt.
> > >
> > > >
> > > > Note that kfree(SCTP_SO(new, i)->ext) shouldn't have the reported
> > > > problem, as at that moment, the "new" stream hasn't been set
> > > > stream_sched yet. It means there's only one place that needs to
> > > > call free_sid in sctp_stream_outq_migrate().
> > > > (Maybe Zhengchao can help us confirm this?)
> > >
> > > That's the case in Tetsuo's patch (earlier today) as well. Yet, if we
> > > have an official way to free a stream, if it's not error handling
> > > during initialization, it should use it.
> > right.
> >
> > >
> > > >
> > > > >
> > > > > > +               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 +340,7 @@ 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,
> > > > > >         .free = sctp_sched_prio_free,
> > > > > >         .enqueue = sctp_sched_prio_enqueue,
> > > > > >         .dequeue = sctp_sched_prio_dequeue,
> > > > > >
> > > > > > then call it in sctp_stream_outq_migrate(), like:
> > > > > >
> > > > > > +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.
> > > > > > @@ -70,16 +79,14 @@ static void sctp_stream_outq_migrate(struct
> > > > > > sctp_stream *stream,
> > > > > >                  * sctp_stream_update will swap ->out pointers.
> > > > > >                  */
> > > > > >                 for (i = 0; i < outcnt; i++) {
> > > > > > -                       kfree(SCTP_SO(new, i)->ext);
> > > > > > +                       sctp_stream_free_ext(new, i);
> > > > > >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> > > > > >                         SCTP_SO(stream, i)->ext = NULL;
> > > > > >                 }
> > > > > >         }
> > > > > >
> > > > > > -       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(new, i);
> > > > > >  }
> > > > > >
> > > > > > Marcelo, do you see a better solution?
> > > > >
> > > > > No. Your suggestion is the best I could think of too.
> > > > >
> > > > > Another approach would be to expose sched->free and do all the freeing
> > > > > at once, like sctp_stream_free() does. But the above is looks cleaner
> > > > > and makes it evident that freeing 'ext' is not trivial.
> > > > >
> > > > > With the proposal above, sctp_sched_prio_free() becomes an
> > > > > optimization, if we can call it that. With the for/if replacement
> > > > > above, not even that, and should be removed. Including sctp_sched_ops
> > > > > 'free' pointer.
> > > > Or we extract the common code to another function, like
> > > > sctp_sched_prio_free_head(stream, prio), and pass prio as
> > > > NULL in sctp_sched_prio_free() for freeing all.
> > > >
> > > > >
> > > > > sctp_stream_free() then should be updated to use the new
> > > > > sctp_stream_free_ext() instead, instead of mangling it directly.
> > > > I thought about this, but there is ".free", which is more efficient
> > > > to free all prio than calling ".free_sid" outcnt times.
> > >
> > > How much more efficient, just by avoiding retpoline stuff on the
> > > indirect functional call or something else?
> >
> > in sctp_stream_free():
> > .free() will be called one time to free all prios
> > while .free_sid will be called in a loop to  free all prios:
> >         for (i = 0; i < stream->outcnt; i++)
> >                .free_sid(stream, i);
> >
> > inside either() .free or . free_sid() there is another loop:
> > for (i = 0; i < stream->outcnt; i++)
> >     ...
> >
> > That's why I said using .free() in sctp_stream_free() will be more efficient.
> >
> > >
> > > >
> > > > I may move free_sid() out of sctp_stream_free_ext(), then in
> > > > sctp_stream_free() we can call sctp_stream_free_ext() without
> > > > calling free_sid(), or just remove sctp_stream_free_ext().
> > >
> > > It's easier to maintain it if we have symmetric paths for initializing
> > > and for freeing it and less special cases. We already have
> > > sctp_stream_init_ext(), so having sctp_stream_free_ext() is not off.
> > didn't notice init_sid in sctp_stream_init_ext(), it makes sense to
> > have free_sid in sctp_stream_free_ext().
> >
> > Thanks.
> >
> > >
> > > I'm happy to review any patch that also updates sctp_stream_free(),
> > > one way or another.
> > >
> > > >
> > > > Thanks.
> > > >
> > > > >
> > > > > Makes sense?
> > > > >
> > > > > Thanks,
> > > > > Marcelo

Re: [PATCH net] sctp: fix memory leak in sctp_stream_outq_migrate()

[Xin Long]

On Wed, Nov 23, 2022 at 2:01 PM Marcelo Ricardo Leitner
<marcelo.leitner@gmail.com> wrote:
>
> On Wed, Nov 23, 2022 at 01:48:01PM -0500, Xin Long wrote:
> > On Wed, Nov 23, 2022 at 1:30 PM Xin Long <lucien.xin@gmail.com> wrote:
> > >
> > > (
> > >
> > > On Wed, Nov 23, 2022 at 1:10 PM Marcelo Ricardo Leitner
> > > <marcelo.leitner@gmail.com> wrote:
> > > >
> > > > On Wed, Nov 23, 2022 at 12:20:44PM -0500, Xin Long wrote:
> > > > > On Tue, Nov 22, 2022 at 6:35 PM Marcelo Ricardo Leitner
> > > > > <marcelo.leitner@gmail.com> wrote:
> > > > > >
> > > > > > On Fri, Nov 18, 2022 at 10:15:50PM -0500, Xin Long wrote:
> > > > > > > On Fri, Nov 18, 2022 at 3:48 AM Zhengchao Shao <shaozhengchao@huawei.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
> > > > > > > >
> > > > > > > > Fixes: 637784ade221 ("sctp: introduce priority based stream scheduler")
> > > > > > > > Reported-by: syzbot+29c402e56c4760763cc0@syzkaller.appspotmail.com
> > > > > > > > Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> > > > > > > > ---
> > > > > > > >  net/sctp/stream.c | 6 ++++++
> > > > > > > >  1 file changed, 6 insertions(+)
> > > > > > > >
> > > > > > > > diff --git a/net/sctp/stream.c b/net/sctp/stream.c
> > > > > > > > index ef9fceadef8d..a17dc368876f 100644
> > > > > > > > --- a/net/sctp/stream.c
> > > > > > > > +++ b/net/sctp/stream.c
> > > > > > > > @@ -70,6 +70,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > > > > > > >                  * sctp_stream_update will swap ->out pointers.
> > > > > > > >                  */
> > > > > > > >                 for (i = 0; i < outcnt; i++) {
> > > > > > > > +                       if (SCTP_SO(new, i)->ext)
> > > > > > > > +                               kfree(SCTP_SO(new, i)->ext->prio_head);
> > > > > > > > +
> > > > > > > >                         kfree(SCTP_SO(new, i)->ext);
> > > > > > > >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> > > > > > > >                         SCTP_SO(stream, i)->ext = NULL;
> > > > > > > > @@ -77,6 +80,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
> > > > > > > >         }
> > > > > > > >
> > > > > > > >         for (i = outcnt; i < stream->outcnt; i++) {
> > > > > > > > +               if (SCTP_SO(stream, i)->ext)
> > > > > > > > +                       kfree(SCTP_SO(stream, i)->ext->prio_head);
> > > > > > > > +
> > > > > > > >                 kfree(SCTP_SO(stream, i)->ext);
> > > > > > > >                 SCTP_SO(stream, i)->ext = NULL;
> > > > > > > >         }
> > > > > > > > --
> > > > > > > > 2.17.1
> > > > > > > >
> > > > > > > This is not a proper fix:
> > > > > > > 1. you shouldn't access "prio_head" outside stream_sched_prio.c.
> > > > > > > 2. the prio_head you freed might be used by other out streams, freeing
> > > > > > > it unconditionally would cause either a double free or use after free.
> > > > > > >
> > > > > > > I'm afraid we have to add a ".free_sid" in sctp_sched_ops, and
> > > > > > > implement it for sctp_sched_prio, like:
> > > > > > >
> > > > > > > +static void sctp_sched_prio_free_sid(struct sctp_stream *stream, __u16 sid)
> > > > > > > +{
> > > > > > > +       struct sctp_stream_priorities *prio = SCTP_SO(stream,
> > > > > > > sid)->ext->prio_head;
> > > > > > > +       int i;
> > > > > > > +
> > > > > > > +       if (!prio)
> > > > > > > +               return;
> > > > > > > +
> > > > > > > +       SCTP_SO(stream, sid)->ext->prio_head = NULL;
> > > > > > > +       for (i = 0; i < stream->outcnt; i++) {
> > > > > >
> > > > > > Instead of checking all streams, the for() can/should be replaced by
> > > > > > (from sctp_sched_prio_free):
> > > > > >         if (!list_empty(&prio->prio_sched))
> > > > > >                 return;
> > > > > sctp_stream_outq_migrate() is called after unsched_all() for "stream",
> > > > > list_empty(prio_sched) is expected to be true.
> > > >
> > > > Good point. Am I missing something or the 'prio_head == prio' below
> > > > would always be false then as well?
> > sorry, forgot to reply to this one :D
>
> :D
>
> >
> > after .unsched_all, multiple outstreams may have the same prio_head,
> > which are not on any list (like stream->prio_list).
> >
> > so when freeing one outstream ext, it will need to go over all outstreams' exts
> > and check if this outstream ext's prio is equal to that of any other outstreams.
>
> Understood. The check in sctp_sched_prio_free() is actually checking
> if the prio_head is not yet scheduled for freeing instead, right.
> Thanks. Hmm. This for() can be quite expensive then. :-(
>
> >
> > > >
> > > > Anyhow, as this is moving to something that can potentially be called
> > > > from other places afterwards, keeping the check doesn't hurt.
> > > >
> > > > >
> > > > > Note that kfree(SCTP_SO(new, i)->ext) shouldn't have the reported
> > > > > problem, as at that moment, the "new" stream hasn't been set
> > > > > stream_sched yet. It means there's only one place that needs to
> > > > > call free_sid in sctp_stream_outq_migrate().
> > > > > (Maybe Zhengchao can help us confirm this?)
> > > >
> > > > That's the case in Tetsuo's patch (earlier today) as well. Yet, if we
> > > > have an official way to free a stream, if it's not error handling
> > > > during initialization, it should use it.
> > > right.
> > >
> > > >
> > > > >
> > > > > >
> > > > > > > +               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 +340,7 @@ 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,
> > > > > > >         .free = sctp_sched_prio_free,
> > > > > > >         .enqueue = sctp_sched_prio_enqueue,
> > > > > > >         .dequeue = sctp_sched_prio_dequeue,
> > > > > > >
> > > > > > > then call it in sctp_stream_outq_migrate(), like:
> > > > > > >
> > > > > > > +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.
> > > > > > > @@ -70,16 +79,14 @@ static void sctp_stream_outq_migrate(struct
> > > > > > > sctp_stream *stream,
> > > > > > >                  * sctp_stream_update will swap ->out pointers.
> > > > > > >                  */
> > > > > > >                 for (i = 0; i < outcnt; i++) {
> > > > > > > -                       kfree(SCTP_SO(new, i)->ext);
> > > > > > > +                       sctp_stream_free_ext(new, i);
> > > > > > >                         SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
> > > > > > >                         SCTP_SO(stream, i)->ext = NULL;
> > > > > > >                 }
> > > > > > >         }
> > > > > > >
> > > > > > > -       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(new, i);
> > > > > > >  }
> > > > > > >
> > > > > > > Marcelo, do you see a better solution?
> > > > > >
> > > > > > No. Your suggestion is the best I could think of too.
> > > > > >
> > > > > > Another approach would be to expose sched->free and do all the freeing
> > > > > > at once, like sctp_stream_free() does. But the above is looks cleaner
> > > > > > and makes it evident that freeing 'ext' is not trivial.
> > > > > >
> > > > > > With the proposal above, sctp_sched_prio_free() becomes an
> > > > > > optimization, if we can call it that. With the for/if replacement
> > > > > > above, not even that, and should be removed. Including sctp_sched_ops
> > > > > > 'free' pointer.
> > > > > Or we extract the common code to another function, like
> > > > > sctp_sched_prio_free_head(stream, prio), and pass prio as
> > > > > NULL in sctp_sched_prio_free() for freeing all.
> > > > >
> > > > > >
> > > > > > sctp_stream_free() then should be updated to use the new
> > > > > > sctp_stream_free_ext() instead, instead of mangling it directly.
> > > > > I thought about this, but there is ".free", which is more efficient
> > > > > to free all prio than calling ".free_sid" outcnt times.
> > > >
> > > > How much more efficient, just by avoiding retpoline stuff on the
> > > > indirect functional call or something else?
> > >
> > > in sctp_stream_free():
> > > .free() will be called one time to free all prios
> > > while .free_sid will be called in a loop to  free all prios:
> > >         for (i = 0; i < stream->outcnt; i++)
> > >                .free_sid(stream, i);
> > >
> > > inside either() .free or . free_sid() there is another loop:
> > > for (i = 0; i < stream->outcnt; i++)
> > >     ...
> > >
> > > That's why I said using .free() in sctp_stream_free() will be more efficient.
> > >
> > > >
> > > > >
> > > > > I may move free_sid() out of sctp_stream_free_ext(), then in
> > > > > sctp_stream_free() we can call sctp_stream_free_ext() without
> > > > > calling free_sid(), or just remove sctp_stream_free_ext().
> > > >
> > > > It's easier to maintain it if we have symmetric paths for initializing
> > > > and for freeing it and less special cases. We already have
> > > > sctp_stream_init_ext(), so having sctp_stream_free_ext() is not off.
> > > didn't notice init_sid in sctp_stream_init_ext(), it makes sense to
> > > have free_sid in sctp_stream_free_ext().
> > >
> > > Thanks.
> > >
> > > >
> > > > I'm happy to review any patch that also updates sctp_stream_free(),
> > > > one way or another.
> > > >
Hi, Zhengchao

Would you please post v2 with the proposal above?
(also add syzkaller-bugs@googlegroups.com into Cc list as Tetsuo
suggested in another thread)

Thanks.

Re: [PATCH net] sctp: fix memory leak in sctp_stream_outq_migrate()

[shaozhengchao]

On 2022/11/24 11:04, Xin Long wrote:
> On Wed, Nov 23, 2022 at 2:01 PM Marcelo Ricardo Leitner
> <marcelo.leitner@gmail.com> wrote:
>>
>> On Wed, Nov 23, 2022 at 01:48:01PM -0500, Xin Long wrote:
>>> On Wed, Nov 23, 2022 at 1:30 PM Xin Long <lucien.xin@gmail.com> wrote:
>>>>
>>>> (
>>>>
>>>> On Wed, Nov 23, 2022 at 1:10 PM Marcelo Ricardo Leitner
>>>> <marcelo.leitner@gmail.com> wrote:
>>>>>
>>>>> On Wed, Nov 23, 2022 at 12:20:44PM -0500, Xin Long wrote:
>>>>>> On Tue, Nov 22, 2022 at 6:35 PM Marcelo Ricardo Leitner
>>>>>> <marcelo.leitner@gmail.com> wrote:
>>>>>>>
>>>>>>> On Fri, Nov 18, 2022 at 10:15:50PM -0500, Xin Long wrote:
>>>>>>>> On Fri, Nov 18, 2022 at 3:48 AM Zhengchao Shao <shaozhengchao@huawei.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
>>>>>>>>>
>>>>>>>>> Fixes: 637784ade221 ("sctp: introduce priority based stream scheduler")
>>>>>>>>> Reported-by: syzbot+29c402e56c4760763cc0@syzkaller.appspotmail.com
>>>>>>>>> Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
>>>>>>>>> ---
>>>>>>>>>   net/sctp/stream.c | 6 ++++++
>>>>>>>>>   1 file changed, 6 insertions(+)
>>>>>>>>>
>>>>>>>>> diff --git a/net/sctp/stream.c b/net/sctp/stream.c
>>>>>>>>> index ef9fceadef8d..a17dc368876f 100644
>>>>>>>>> --- a/net/sctp/stream.c
>>>>>>>>> +++ b/net/sctp/stream.c
>>>>>>>>> @@ -70,6 +70,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
>>>>>>>>>                   * sctp_stream_update will swap ->out pointers.
>>>>>>>>>                   */
>>>>>>>>>                  for (i = 0; i < outcnt; i++) {
>>>>>>>>> +                       if (SCTP_SO(new, i)->ext)
>>>>>>>>> +                               kfree(SCTP_SO(new, i)->ext->prio_head);
>>>>>>>>> +
>>>>>>>>>                          kfree(SCTP_SO(new, i)->ext);
>>>>>>>>>                          SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
>>>>>>>>>                          SCTP_SO(stream, i)->ext = NULL;
>>>>>>>>> @@ -77,6 +80,9 @@ static void sctp_stream_outq_migrate(struct sctp_stream *stream,
>>>>>>>>>          }
>>>>>>>>>
>>>>>>>>>          for (i = outcnt; i < stream->outcnt; i++) {
>>>>>>>>> +               if (SCTP_SO(stream, i)->ext)
>>>>>>>>> +                       kfree(SCTP_SO(stream, i)->ext->prio_head);
>>>>>>>>> +
>>>>>>>>>                  kfree(SCTP_SO(stream, i)->ext);
>>>>>>>>>                  SCTP_SO(stream, i)->ext = NULL;
>>>>>>>>>          }
>>>>>>>>> --
>>>>>>>>> 2.17.1
>>>>>>>>>
>>>>>>>> This is not a proper fix:
>>>>>>>> 1. you shouldn't access "prio_head" outside stream_sched_prio.c.
>>>>>>>> 2. the prio_head you freed might be used by other out streams, freeing
>>>>>>>> it unconditionally would cause either a double free or use after free.
>>>>>>>>
>>>>>>>> I'm afraid we have to add a ".free_sid" in sctp_sched_ops, and
>>>>>>>> implement it for sctp_sched_prio, like:
>>>>>>>>
>>>>>>>> +static void sctp_sched_prio_free_sid(struct sctp_stream *stream, __u16 sid)
>>>>>>>> +{
>>>>>>>> +       struct sctp_stream_priorities *prio = SCTP_SO(stream,
>>>>>>>> sid)->ext->prio_head;
>>>>>>>> +       int i;
>>>>>>>> +
>>>>>>>> +       if (!prio)
>>>>>>>> +               return;
>>>>>>>> +
>>>>>>>> +       SCTP_SO(stream, sid)->ext->prio_head = NULL;
>>>>>>>> +       for (i = 0; i < stream->outcnt; i++) {
>>>>>>>
>>>>>>> Instead of checking all streams, the for() can/should be replaced by
>>>>>>> (from sctp_sched_prio_free):
>>>>>>>          if (!list_empty(&prio->prio_sched))
>>>>>>>                  return;
>>>>>> sctp_stream_outq_migrate() is called after unsched_all() for "stream",
>>>>>> list_empty(prio_sched) is expected to be true.
>>>>>
>>>>> Good point. Am I missing something or the 'prio_head == prio' below
>>>>> would always be false then as well?
>>> sorry, forgot to reply to this one :D
>>
>> :D
>>
>>>
>>> after .unsched_all, multiple outstreams may have the same prio_head,
>>> which are not on any list (like stream->prio_list).
>>>
>>> so when freeing one outstream ext, it will need to go over all outstreams' exts
>>> and check if this outstream ext's prio is equal to that of any other outstreams.
>>
>> Understood. The check in sctp_sched_prio_free() is actually checking
>> if the prio_head is not yet scheduled for freeing instead, right.
>> Thanks. Hmm. This for() can be quite expensive then. :-(
>>
>>>
>>>>>
>>>>> Anyhow, as this is moving to something that can potentially be called
>>>>> from other places afterwards, keeping the check doesn't hurt.
>>>>>
>>>>>>
>>>>>> Note that kfree(SCTP_SO(new, i)->ext) shouldn't have the reported
>>>>>> problem, as at that moment, the "new" stream hasn't been set
>>>>>> stream_sched yet. It means there's only one place that needs to
>>>>>> call free_sid in sctp_stream_outq_migrate().
>>>>>> (Maybe Zhengchao can help us confirm this?)
>>>>>
>>>>> That's the case in Tetsuo's patch (earlier today) as well. Yet, if we
>>>>> have an official way to free a stream, if it's not error handling
>>>>> during initialization, it should use it.
>>>> right.
>>>>
>>>>>
>>>>>>
>>>>>>>
>>>>>>>> +               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 +340,7 @@ 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,
>>>>>>>>          .free = sctp_sched_prio_free,
>>>>>>>>          .enqueue = sctp_sched_prio_enqueue,
>>>>>>>>          .dequeue = sctp_sched_prio_dequeue,
>>>>>>>>
>>>>>>>> then call it in sctp_stream_outq_migrate(), like:
>>>>>>>>
>>>>>>>> +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.
>>>>>>>> @@ -70,16 +79,14 @@ static void sctp_stream_outq_migrate(struct
>>>>>>>> sctp_stream *stream,
>>>>>>>>                   * sctp_stream_update will swap ->out pointers.
>>>>>>>>                   */
>>>>>>>>                  for (i = 0; i < outcnt; i++) {
>>>>>>>> -                       kfree(SCTP_SO(new, i)->ext);
>>>>>>>> +                       sctp_stream_free_ext(new, i);
>>>>>>>>                          SCTP_SO(new, i)->ext = SCTP_SO(stream, i)->ext;
>>>>>>>>                          SCTP_SO(stream, i)->ext = NULL;
>>>>>>>>                  }
>>>>>>>>          }
>>>>>>>>
>>>>>>>> -       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(new, i);
>>>>>>>>   }
>>>>>>>>
>>>>>>>> Marcelo, do you see a better solution?
>>>>>>>
>>>>>>> No. Your suggestion is the best I could think of too.
>>>>>>>
>>>>>>> Another approach would be to expose sched->free and do all the freeing
>>>>>>> at once, like sctp_stream_free() does. But the above is looks cleaner
>>>>>>> and makes it evident that freeing 'ext' is not trivial.
>>>>>>>
>>>>>>> With the proposal above, sctp_sched_prio_free() becomes an
>>>>>>> optimization, if we can call it that. With the for/if replacement
>>>>>>> above, not even that, and should be removed. Including sctp_sched_ops
>>>>>>> 'free' pointer.
>>>>>> Or we extract the common code to another function, like
>>>>>> sctp_sched_prio_free_head(stream, prio), and pass prio as
>>>>>> NULL in sctp_sched_prio_free() for freeing all.
>>>>>>
>>>>>>>
>>>>>>> sctp_stream_free() then should be updated to use the new
>>>>>>> sctp_stream_free_ext() instead, instead of mangling it directly.
>>>>>> I thought about this, but there is ".free", which is more efficient
>>>>>> to free all prio than calling ".free_sid" outcnt times.
>>>>>
>>>>> How much more efficient, just by avoiding retpoline stuff on the
>>>>> indirect functional call or something else?
>>>>
>>>> in sctp_stream_free():
>>>> .free() will be called one time to free all prios
>>>> while .free_sid will be called in a loop to  free all prios:
>>>>          for (i = 0; i < stream->outcnt; i++)
>>>>                 .free_sid(stream, i);
>>>>
>>>> inside either() .free or . free_sid() there is another loop:
>>>> for (i = 0; i < stream->outcnt; i++)
>>>>      ...
>>>>
>>>> That's why I said using .free() in sctp_stream_free() will be more efficient.
>>>>
>>>>>
>>>>>>
>>>>>> I may move free_sid() out of sctp_stream_free_ext(), then in
>>>>>> sctp_stream_free() we can call sctp_stream_free_ext() without
>>>>>> calling free_sid(), or just remove sctp_stream_free_ext().
>>>>>
>>>>> It's easier to maintain it if we have symmetric paths for initializing
>>>>> and for freeing it and less special cases. We already have
>>>>> sctp_stream_init_ext(), so having sctp_stream_free_ext() is not off.
>>>> didn't notice init_sid in sctp_stream_init_ext(), it makes sense to
>>>> have free_sid in sctp_stream_free_ext().
>>>>
>>>> Thanks.
>>>>
>>>>>
>>>>> I'm happy to review any patch that also updates sctp_stream_free(),
>>>>> one way or another.
>>>>>
> Hi, Zhengchao
> 
> Would you please post v2 with the proposal above?
> (also add syzkaller-bugs@googlegroups.com into Cc list as Tetsuo
> suggested in another thread)
> 
> Thanks.

OK， I will send V2 as soon as I have tested patch.

Zhengchao Shao