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authorXin Long <lucien.xin@gmail.com>2023-02-22 20:07:21 +0300
committerJakub Kicinski <kuba@kernel.org>2023-02-23 23:59:40 +0300
commit68ba44639537de6f91fe32783766322d41848127 (patch)
tree222dc61d66f8b3daf6ea07050ca7806cac009ad9 /net/sctp/stream_sched_prio.c
parentee0a735fd97ccde766ab557d1fc722c92cebacda (diff)
downloadlinux-68ba44639537de6f91fe32783766322d41848127.tar.xz
sctp: add a refcnt in sctp_stream_priorities to avoid a nested loop
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@redhat.com> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> Signed-off-by: Xin Long <lucien.xin@gmail.com> Link: https://lore.kernel.org/r/825eb0c905cb864991eba335f4a2b780e543f06b.1677085641.git.lucien.xin@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/sctp/stream_sched_prio.c')
-rw-r--r--net/sctp/stream_sched_prio.c52
1 files changed, 21 insertions, 31 deletions
diff --git a/net/sctp/stream_sched_prio.c b/net/sctp/stream_sched_prio.c
index 42d4800f263d..4d4d9da331f4 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_enqueue(struct sctp_outq *q,