This is a note to let you know that I've just added the patch titled
sctp: add a refcnt in sctp_stream_priorities to avoid a nested loop
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sctp-add-a-refcnt-in-sctp_stream_priorities-to-avoid.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 0da1fbfb33d87c3907cb788aca6971be52239332
Author: Xin Long <lucien.xin@xxxxxxxxx>
Date: Wed Feb 22 12:07:21 2023 -0500
sctp: add a refcnt in sctp_stream_priorities to avoid a nested loop
[ Upstream commit 68ba44639537de6f91fe32783766322d41848127 ]
With this refcnt added in sctp_stream_priorities, we don't need to
traverse all streams to check if the prio is used by other streams
when freeing one stream's prio in sctp_sched_prio_free_sid(). This
can avoid a nested loop (up to 65535 * 65535), which may cause a
stuck as Ying reported:
watchdog: BUG: soft lockup - CPU#23 stuck for 26s! [ksoftirqd/23:136]
Call Trace:
<TASK>
sctp_sched_prio_free_sid+0xab/0x100 [sctp]
sctp_stream_free_ext+0x64/0xa0 [sctp]
sctp_stream_free+0x31/0x50 [sctp]
sctp_association_free+0xa5/0x200 [sctp]
Note that it doesn't need to use refcount_t type for this counter,
as its accessing is always protected under the sock lock.
v1->v2:
- add a check in sctp_sched_prio_set to avoid the possible prio_head
refcnt overflow.
Fixes: 9ed7bfc79542 ("sctp: fix memory leak in sctp_stream_outq_migrate()")
Reported-by: Ying Xu <yinxu@xxxxxxxxxx>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Link: https://lore.kernel.org/r/825eb0c905cb864991eba335f4a2b780e543f06b.1677085641.git.lucien.xin@xxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/net/sctp/structs.h b/include/net/sctp/structs.h
index cb05e503c9cd1..48cbf3352042f 100644
--- a/include/net/sctp/structs.h
+++ b/include/net/sctp/structs.h
@@ -1400,6 +1400,7 @@ struct sctp_stream_priorities {
/* The next stream stream in line */
struct sctp_stream_out_ext *next;
__u16 prio;
+ __u16 users;
};
struct sctp_stream_out_ext {
diff --git a/net/sctp/stream_sched_prio.c b/net/sctp/stream_sched_prio.c
index 4fc9f2923ed11..7dd9f8b387cca 100644
--- a/net/sctp/stream_sched_prio.c
+++ b/net/sctp/stream_sched_prio.c
@@ -25,6 +25,18 @@
static void sctp_sched_prio_unsched_all(struct sctp_stream *stream);
+static struct sctp_stream_priorities *sctp_sched_prio_head_get(struct sctp_stream_priorities *p)
+{
+ p->users++;
+ return p;
+}
+
+static void sctp_sched_prio_head_put(struct sctp_stream_priorities *p)
+{
+ if (p && --p->users == 0)
+ kfree(p);
+}
+
static struct sctp_stream_priorities *sctp_sched_prio_new_head(
struct sctp_stream *stream, int prio, gfp_t gfp)
{
@@ -38,6 +50,7 @@ static struct sctp_stream_priorities *sctp_sched_prio_new_head(
INIT_LIST_HEAD(&p->active);
p->next = NULL;
p->prio = prio;
+ p->users = 1;
return p;
}
@@ -53,7 +66,7 @@ static struct sctp_stream_priorities *sctp_sched_prio_get_head(
*/
list_for_each_entry(p, &stream->prio_list, prio_sched) {
if (p->prio == prio)
- return p;
+ return sctp_sched_prio_head_get(p);
if (p->prio > prio)
break;
}
@@ -70,7 +83,7 @@ static struct sctp_stream_priorities *sctp_sched_prio_get_head(
*/
break;
if (p->prio == prio)
- return p;
+ return sctp_sched_prio_head_get(p);
}
/* If not even there, allocate a new one. */
@@ -154,32 +167,21 @@ static int sctp_sched_prio_set(struct sctp_stream *stream, __u16 sid,
struct sctp_stream_out_ext *soute = sout->ext;
struct sctp_stream_priorities *prio_head, *old;
bool reschedule = false;
- int i;
+
+ old = soute->prio_head;
+ if (old && old->prio == prio)
+ return 0;
prio_head = sctp_sched_prio_get_head(stream, prio, gfp);
if (!prio_head)
return -ENOMEM;
reschedule = sctp_sched_prio_unsched(soute);
- old = soute->prio_head;
soute->prio_head = prio_head;
if (reschedule)
sctp_sched_prio_sched(stream, soute);
- if (!old)
- /* Happens when we set the priority for the first time */
- return 0;
-
- for (i = 0; i < stream->outcnt; i++) {
- soute = SCTP_SO(stream, i)->ext;
- if (soute && soute->prio_head == old)
- /* It's still in use, nothing else to do here. */
- return 0;
- }
-
- /* No hits, we are good to free it. */
- kfree(old);
-
+ sctp_sched_prio_head_put(old);
return 0;
}
@@ -206,20 +208,8 @@ static int sctp_sched_prio_init_sid(struct sctp_stream *stream, __u16 sid,
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_sched_prio_head_put(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)
