[PATCH net 2/2] sch_htb: Fix offload cleanup in htb_destroy on htb_init failure
From: Maxim Mikityanskiy <hidden>
Date: 2021-03-11 14:43:11
Subsystem:
networking [general], tc subsystem, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Jamal Hadi Salim, Jiri Pirko, Linus Torvalds
htb_init may fail to do the offload if it's not supported or if a
runtime error happens when allocating direct qdiscs. In those cases
TC_HTB_CREATE command is not sent to the driver, however, htb_destroy
gets called anyway and attempts to send TC_HTB_DESTROY.
It shouldn't happen, because the driver didn't receive TC_HTB_CREATE,
and also because the driver may not support ndo_setup_tc at all, while
q->offload is true, and htb_destroy mistakenly thinks the offload is
supported. Trying to call ndo_setup_tc in the latter case will lead to a
NULL pointer dereference.
This commit fixes the issues with htb_destroy by deferring assignment of
q->offload until after the TC_HTB_CREATE command. The necessary cleanup
of the offload entities is already done in htb_init.
Reported-by: syzbot+b53a709f04722ca12a3c@syzkaller.appspotmail.com
Fixes: d03b195b5aa0 ("sch_htb: Hierarchical QoS hardware offload")
Suggested-by: Eric Dumazet <redacted>
Signed-off-by: Maxim Mikityanskiy <redacted>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
---
net/sched/sch_htb.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index b23203159996..62e12cb41a3e 100644
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c@@ -1020,6 +1020,7 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt, struct nlattr *tb[TCA_HTB_MAX + 1]; struct tc_htb_glob *gopt; unsigned int ntx; + bool offload; int err; qdisc_watchdog_init(&q->watchdog, sch);
@@ -1044,9 +1045,9 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt, if (gopt->version != HTB_VER >> 16) return -EINVAL; - q->offload = nla_get_flag(tb[TCA_HTB_OFFLOAD]); + offload = nla_get_flag(tb[TCA_HTB_OFFLOAD]); - if (q->offload) { + if (offload) { if (sch->parent != TC_H_ROOT) return -EOPNOTSUPP;
@@ -1076,7 +1077,7 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt, q->rate2quantum = 1; q->defcls = gopt->defcls; - if (!q->offload) + if (!offload) return 0; for (ntx = 0; ntx < q->num_direct_qdiscs; ntx++) {
@@ -1107,12 +1108,14 @@ static int htb_init(struct Qdisc *sch, struct nlattr *opt, if (err) goto err_free_qdiscs; + /* Defer this assignment, so that htb_destroy skips offload-related + * parts (especially calling ndo_setup_tc) on errors. + */ + q->offload = true; + return 0; err_free_qdiscs: - /* TC_HTB_CREATE call failed, avoid any further calls to the driver. */ - q->offload = false; - for (ntx = 0; ntx < q->num_direct_qdiscs && q->direct_qdiscs[ntx]; ntx++) qdisc_put(q->direct_qdiscs[ntx]);
--
2.25.1