| Message ID | 20240805135145.37604-1-dmantipov@yandex.ru (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | net: sched: fix use-after-free in taprio_change() | expand |
Hi, Dmitry Antipov <dmantipov@yandex.ru> writes: > In 'taprio_change()', 'admin' pointer may become dangling due to sched > switch / removal caused by 'advance_sched()', and critical section > protected by 'q->current_entry_lock' is too small to prevent from such > a scenario (which causes use-after-free detected by KASAN). Fix this > by prefer 'rcu_replace_pointer()' over 'rcu_assign_pointer()' to update > 'admin' immediately before an attempt to schedule freeing. > > Fixes: a3d43c0d56f1 ("taprio: Add support adding an admin schedule") > Reported-by: syzbot+b65e0af58423fc8a73aa@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=b65e0af58423fc8a73aa > Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> > --- > net/sched/sch_taprio.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c > index cc2df9f8c14a..59fad74d5ff9 100644 > --- a/net/sched/sch_taprio.c > +++ b/net/sched/sch_taprio.c > @@ -1963,7 +1963,8 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt, > > taprio_start_sched(sch, start, new_admin); > > - rcu_assign_pointer(q->admin_sched, new_admin); > + admin = rcu_replace_pointer(q->admin_sched, new_admin, > + lockdep_rtnl_is_held()); What I am thinking if, for consistency, the same change could be applied to the other branch of this comparison (the txtime one). Could be a separate patch, as the txtime branch is not going to race with advance_sched(). For this patch: Acked-by: Vinicius Costa Gomes <vinicius.gomes@intel.com> Cheers,
diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index cc2df9f8c14a..59fad74d5ff9 100644 --- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c @@ -1963,7 +1963,8 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt, taprio_start_sched(sch, start, new_admin); - rcu_assign_pointer(q->admin_sched, new_admin); + admin = rcu_replace_pointer(q->admin_sched, new_admin, + lockdep_rtnl_is_held()); if (admin) call_rcu(&admin->rcu, taprio_free_sched_cb);
In 'taprio_change()', 'admin' pointer may become dangling due to sched switch / removal caused by 'advance_sched()', and critical section protected by 'q->current_entry_lock' is too small to prevent from such a scenario (which causes use-after-free detected by KASAN). Fix this by prefer 'rcu_replace_pointer()' over 'rcu_assign_pointer()' to update 'admin' immediately before an attempt to schedule freeing. Fixes: a3d43c0d56f1 ("taprio: Add support adding an admin schedule") Reported-by: syzbot+b65e0af58423fc8a73aa@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=b65e0af58423fc8a73aa Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru> --- net/sched/sch_taprio.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)