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Message-ID: <20210311144206.2135872-3-maximmi@nvidia.com>
Date: Thu, 11 Mar 2021 16:42:06 +0200
From: Maxim Mikityanskiy <maximmi@...dia.com>
To: Jamal Hadi Salim <jhs@...atatu.com>,
Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>
CC: "David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Tariq Toukan <tariqt@...dia.com>,
Eric Dumazet <eric.dumazet@...il.com>,
<netdev@...r.kernel.org>, Maxim Mikityanskiy <maximmi@...dia.com>,
<syzbot+b53a709f04722ca12a3c@...kaller.appspotmail.com>
Subject: [PATCH net 2/2] sch_htb: Fix offload cleanup in htb_destroy on htb_init failure
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@...kaller.appspotmail.com
Fixes: d03b195b5aa0 ("sch_htb: Hierarchical QoS hardware offload")
Suggested-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Maxim Mikityanskiy <maximmi@...dia.com>
Reviewed-by: Tariq Toukan <tariqt@...dia.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
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