sctp: fix memory leak in sctp_stream_outq_migrate()

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: 637784ad ("sctp: introduce priority based stream scheduler")
Reported-by: syzbot+29c402e56c4760763cc0@syzkaller.appspotmail.com
Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
Reviewed-by: Xin Long <lucien.xin@gmail.com>
Link: https://lore.kernel.org/r/20221126031720.378562-1-shaozhengchao@huawei.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

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);
 

net/sctp/stream.c

@@ -52,6 +52,19 @@ 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;
+
+	if (!SCTP_SO(stream, sid)->ext)
+		return;
+
+	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 +83,14 @@ 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(stream, i);
 }
 
 static int sctp_stream_alloc_out(struct sctp_stream *stream, __u16 outcnt,
@@ -174,9 +185,9 @@ void sctp_stream_free(struct sctp_stream *stream)
 	struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
 	int i;
 
-	sched->free(stream);
+	sched->unsched_all(stream);
 	for (i = 0; i < stream->outcnt; i++)
-		kfree(SCTP_SO(stream, i)->ext);
+		sctp_stream_free_ext(stream, i);
 	genradix_free(&stream->out);
 	genradix_free(&stream->in);
 }

net/sctp/stream_sched.c

@@ -46,6 +46,10 @@ static int sctp_sched_fcfs_init_sid(struct sctp_stream *stream, __u16 sid,
 	return 0;
 }
 
+static void sctp_sched_fcfs_free_sid(struct sctp_stream *stream, __u16 sid)
+{
+}
+
 static void sctp_sched_fcfs_free(struct sctp_stream *stream)
 {
 }
@@ -96,6 +100,7 @@ static struct sctp_sched_ops sctp_sched_fcfs = {
 	.get = sctp_sched_fcfs_get,
 	.init = sctp_sched_fcfs_init,
 	.init_sid = sctp_sched_fcfs_init_sid,
+	.free_sid = sctp_sched_fcfs_free_sid,
 	.free = sctp_sched_fcfs_free,
 	.enqueue = sctp_sched_fcfs_enqueue,
 	.dequeue = sctp_sched_fcfs_dequeue,

net/sctp/stream_sched_prio.c

@@ -204,6 +204,24 @@ 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 = 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 +341,7 @@ 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,

net/sctp/stream_sched_rr.c

@@ -90,6 +90,10 @@ static int sctp_sched_rr_init_sid(struct sctp_stream *stream, __u16 sid,
 	return 0;
 }
 
+static void sctp_sched_rr_free_sid(struct sctp_stream *stream, __u16 sid)
+{
+}
+
 static void sctp_sched_rr_free(struct sctp_stream *stream)
 {
 	sctp_sched_rr_unsched_all(stream);
@@ -177,6 +181,7 @@ static struct sctp_sched_ops sctp_sched_rr = {
 	.get = sctp_sched_rr_get,
 	.init = sctp_sched_rr_init,
 	.init_sid = sctp_sched_rr_init_sid,
+	.free_sid = sctp_sched_rr_free_sid,
 	.free = sctp_sched_rr_free,
 	.enqueue = sctp_sched_rr_enqueue,
 	.dequeue = sctp_sched_rr_dequeue,