From b3fd8fa1cae7837043bfb1096c413a086f720a4b Mon Sep 17 00:00:00 2001
From: Daan De Meyer <daan.j.demeyer@gmail.com>
Date: Wed, 1 May 2024 14:41:41 +0200
Subject: [PATCH 0611/1160] network/tc: Avoid concurrent set modification in
tclass_drop()/qdisc_drop()
With the current algorithm, we can end up removing entries from the
qdisc/tclass sets while having multiple open iterators over the sets at
various positions which leads to assertion failures in the hashmap logic
as it's only safe to remove the "current" entry.
To avoid the problem, let's split up marking and dropping of tclasses
and qdiscs. First, we recursively iterate tclasses/qdiscs and mark all
that need to be removed. Next, we iterate once over tclasses and qdiscs
and remove all marked entries.
Fixes 632d321050f58fe1b5bed7cfe769d212377c0301
(cherry picked from commit ee8f605ded4fea6b93aae018415efae877c26ed2)
src/network/tc/qdisc.c | 54 ++++++++++++++++++++++++++++-------------
src/network/tc/qdisc.h | 2 ++
src/network/tc/tclass.c | 53 +++++++++++++++++++++++++++-------------
src/network/tc/tclass.h | 2 ++
4 files changed, 77 insertions(+), 34 deletions(-)
@@ -285,37 +285,57 @@ int link_find_qdisc(Link *link, uint32_t handle, const char *kind, QDisc **ret)
return -ENOENT;
}
-QDisc* qdisc_drop(QDisc *qdisc) {
+void qdisc_mark_recursive(QDisc *qdisc) {
TClass *tclass;
- Link *link;
assert(qdisc);
+ assert(qdisc->link);
- link = ASSERT_PTR(qdisc->link);
+ if (qdisc_is_marked(qdisc))
+ return;
- qdisc_mark(qdisc); /* To avoid stack overflow. */
+ qdisc_mark(qdisc);
- /* also drop all child classes assigned to the qdisc. */
- SET_FOREACH(tclass, link->tclasses) {
- if (tclass_is_marked(tclass))
+ /* also mark all child classes assigned to the qdisc. */
+ SET_FOREACH(tclass, qdisc->link->tclasses) {
+ if (TC_H_MAJ(tclass->classid) != qdisc->handle)
continue;
- if (TC_H_MAJ(tclass->classid) != qdisc->handle)
+ tclass_mark_recursive(tclass);
+ }
+}
+
+void link_qdisc_drop_marked(Link *link) {
+ QDisc *qdisc;
+
+ assert(link);
+
+ SET_FOREACH(qdisc, link->qdiscs) {
+ if (!qdisc_is_marked(qdisc))
continue;
- tclass_drop(tclass);
+ qdisc_unmark(qdisc);
+ qdisc_enter_removed(qdisc);
+
+ if (qdisc->state == 0) {
+ log_qdisc_debug(qdisc, link, "Forgetting");
+ qdisc_free(qdisc);
+ } else
+ log_qdisc_debug(qdisc, link, "Removed");
}
+}
- qdisc_unmark(qdisc);
- qdisc_enter_removed(qdisc);
+QDisc* qdisc_drop(QDisc *qdisc) {
+ assert(qdisc);
+ assert(qdisc->link);
- if (qdisc->state == 0) {
- log_qdisc_debug(qdisc, link, "Forgetting");
- qdisc = qdisc_free(qdisc);
- } else
- log_qdisc_debug(qdisc, link, "Removed");
+ qdisc_mark_recursive(qdisc);
+
+ /* link_qdisc_drop_marked() may invalidate qdisc, so run link_tclass_drop_marked() first. */
+ link_tclass_drop_marked(qdisc->link);
+ link_qdisc_drop_marked(qdisc->link);
- return qdisc;
+ return NULL;
}
static int qdisc_handler(sd_netlink *rtnl, sd_netlink_message *m, Request *req, Link *link, QDisc *qdisc) {
@@ -77,7 +77,9 @@ DEFINE_NETWORK_CONFIG_STATE_FUNCTIONS(QDisc, qdisc);
QDisc* qdisc_free(QDisc *qdisc);
int qdisc_new_static(QDiscKind kind, Network *network, const char *filename, unsigned section_line, QDisc **ret);
+void qdisc_mark_recursive(QDisc *qdisc);
QDisc* qdisc_drop(QDisc *qdisc);
+void link_qdisc_drop_marked(Link *link);
int link_find_qdisc(Link *link, uint32_t handle, const char *kind, QDisc **qdisc);
@@ -252,37 +252,56 @@ static void log_tclass_debug(TClass *tclass, Link *link, const char *str) {
strna(tclass_get_tca_kind(tclass)));
}
-TClass* tclass_drop(TClass *tclass) {
+void tclass_mark_recursive(TClass *tclass) {
QDisc *qdisc;
- Link *link;
assert(tclass);
+ assert(tclass->link);
- link = ASSERT_PTR(tclass->link);
+ if (tclass_is_marked(tclass))
+ return;
- tclass_mark(tclass); /* To avoid stack overflow. */
+ tclass_mark(tclass);
- /* Also drop all child qdiscs assigned to the class. */
- SET_FOREACH(qdisc, link->qdiscs) {
- if (qdisc_is_marked(qdisc))
+ /* Also mark all child qdiscs assigned to the class. */
+ SET_FOREACH(qdisc, tclass->link->qdiscs) {
+ if (qdisc->parent != tclass->classid)
continue;
- if (qdisc->parent != tclass->classid)
+ qdisc_mark_recursive(qdisc);
+ }
+}
+
+void link_tclass_drop_marked(Link *link) {
+ TClass *tclass;
+
+ assert(link);
+
+ SET_FOREACH(tclass, link->tclasses) {
+ if (!tclass_is_marked(tclass))
continue;
- qdisc_drop(qdisc);
+ tclass_unmark(tclass);
+ tclass_enter_removed(tclass);
+
+ if (tclass->state == 0) {
+ log_tclass_debug(tclass, link, "Forgetting");
+ tclass_free(tclass);
+ } else
+ log_tclass_debug(tclass, link, "Removed");
}
+}
- tclass_unmark(tclass);
- tclass_enter_removed(tclass);
+TClass* tclass_drop(TClass *tclass) {
+ assert(tclass);
- if (tclass->state == 0) {
- log_tclass_debug(tclass, link, "Forgetting");
- tclass = tclass_free(tclass);
- } else
- log_tclass_debug(tclass, link, "Removed");
+ tclass_mark_recursive(tclass);
+
+ /* link_tclass_drop_marked() may invalidate tclass, so run link_qdisc_drop_marked() first. */
+ link_qdisc_drop_marked(tclass->link);
+ link_tclass_drop_marked(tclass->link);
- return tclass;
+ return NULL;
}
static int tclass_handler(sd_netlink *rtnl, sd_netlink_message *m, Request *req, Link *link, TClass *tclass) {
@@ -58,7 +58,9 @@ DEFINE_NETWORK_CONFIG_STATE_FUNCTIONS(TClass, tclass);
TClass* tclass_free(TClass *tclass);
int tclass_new_static(TClassKind kind, Network *network, const char *filename, unsigned section_line, TClass **ret);
+void tclass_mark_recursive(TClass *tclass);
TClass* tclass_drop(TClass *tclass);
+void link_tclass_drop_marked(Link *link);
int link_find_tclass(Link *link, uint32_t classid, TClass **ret);
--
2.33.0