@@ -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]);
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 <eric.dumazet@gmail.com> Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com> Reviewed-by: Tariq Toukan <tariqt@nvidia.com> --- net/sched/sch_htb.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)