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Wed, 15 Jan 2025 20:36:47 -0800 (PST) Date: Wed, 15 Jan 2025 20:36:46 -0800 From: Cong Wang To: Jamal Hadi Salim Cc: Petr Machata , netdev@vger.kernel.org, jiri@resnulli.us, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, petrm@mellanox.com, security@kernel.org, g1042620637@gmail.com Subject: Re: [PATCH net v4 1/1] net: sched: fix ets qdisc OOB Indexing Message-ID: References: <20250111145740.74755-1-jhs@mojatatu.com> <87zfjvqa6w.fsf@nvidia.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Jan 13, 2025 at 06:47:02AM -0500, Jamal Hadi Salim wrote: > On Mon, Jan 13, 2025 at 5:29 AM Petr Machata wrote: > > > > > > Cong Wang writes: > > > > > On Sat, Jan 11, 2025 at 09:57:39AM -0500, Jamal Hadi Salim wrote: > > >> diff --git a/net/sched/sch_ets.c b/net/sched/sch_ets.c > > >> index f80bc05d4c5a..516038a44163 100644 > > >> --- a/net/sched/sch_ets.c > > >> +++ b/net/sched/sch_ets.c > > >> @@ -91,6 +91,8 @@ ets_class_from_arg(struct Qdisc *sch, unsigned long arg) > > >> { > > >> struct ets_sched *q = qdisc_priv(sch); > > >> > > >> + if (arg == 0 || arg > q->nbands) > > >> + return NULL; > > >> return &q->classes[arg - 1]; > > >> } > > > > > > I must miss something here. Some callers of this function don't handle > > > NULL at all, so are you sure it is safe to return NULL for all the > > > callers here?? > > > > > > For one quick example: > > > > > > 322 static int ets_class_dump_stats(struct Qdisc *sch, unsigned long arg, > > > 323 struct gnet_dump *d) > > > 324 { > > > 325 struct ets_class *cl = ets_class_from_arg(sch, arg); > > > 326 struct Qdisc *cl_q = cl->qdisc; > > > > > > 'cl' is not checked against NULL before dereferencing it. > > > > > > There are other cases too, please ensure _all_ of them handle NULL > > > correctly. > > > > Yeah, I looked through ets_class_from_arg() callers last week and I > > think that besides the one call that needs patching, which already > > handles NULL, in all other cases the arg passed to ets_class_from_arg() > > comes from class_find, and therefore shouldn't cause the NULL return. > > Exactly. > Regardless - once the nodes are created we are guaranteed non-null. > See other qdiscs, not just ets. The anti-pattern part is that we usually pass the pointer instead of classid with these 'arg', hence it is unsigned long. In fact, for ->change(), classid is passed as the 2nd parameter, not the 5th. The pointer should come from the return value of ->find(). Something like the untested patch below. Thanks. ----> diff --git a/net/sched/sch_ets.c b/net/sched/sch_ets.c index f80bc05d4c5a..3b7253e8756f 100644 --- a/net/sched/sch_ets.c +++ b/net/sched/sch_ets.c @@ -86,12 +86,9 @@ static int ets_quantum_parse(struct Qdisc *sch, const struct nlattr *attr, return 0; } -static struct ets_class * -ets_class_from_arg(struct Qdisc *sch, unsigned long arg) +static struct ets_class *ets_class_from_arg(unsigned long arg) { - struct ets_sched *q = qdisc_priv(sch); - - return &q->classes[arg - 1]; + return (struct ets_class *) arg; } static u32 ets_class_id(struct Qdisc *sch, const struct ets_class *cl) @@ -198,7 +195,7 @@ static int ets_class_change(struct Qdisc *sch, u32 classid, u32 parentid, struct nlattr **tca, unsigned long *arg, struct netlink_ext_ack *extack) { - struct ets_class *cl = ets_class_from_arg(sch, *arg); + struct ets_class *cl = ets_class_from_arg(*arg); struct ets_sched *q = qdisc_priv(sch); struct nlattr *opt = tca[TCA_OPTIONS]; struct nlattr *tb[TCA_ETS_MAX + 1]; @@ -248,7 +245,7 @@ static int ets_class_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new, struct Qdisc **old, struct netlink_ext_ack *extack) { - struct ets_class *cl = ets_class_from_arg(sch, arg); + struct ets_class *cl = ets_class_from_arg(arg); if (!new) { new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops, @@ -266,7 +263,7 @@ static int ets_class_graft(struct Qdisc *sch, unsigned long arg, static struct Qdisc *ets_class_leaf(struct Qdisc *sch, unsigned long arg) { - struct ets_class *cl = ets_class_from_arg(sch, arg); + struct ets_class *cl = ets_class_from_arg(arg); return cl->qdisc; } @@ -278,12 +275,12 @@ static unsigned long ets_class_find(struct Qdisc *sch, u32 classid) if (band - 1 >= q->nbands) return 0; - return band; + return (unsigned long)&q->classes[band - 1]; } static void ets_class_qlen_notify(struct Qdisc *sch, unsigned long arg) { - struct ets_class *cl = ets_class_from_arg(sch, arg); + struct ets_class *cl = ets_class_from_arg(arg); struct ets_sched *q = qdisc_priv(sch); /* We get notified about zero-length child Qdiscs as well if they are @@ -297,7 +294,7 @@ static void ets_class_qlen_notify(struct Qdisc *sch, unsigned long arg) static int ets_class_dump(struct Qdisc *sch, unsigned long arg, struct sk_buff *skb, struct tcmsg *tcm) { - struct ets_class *cl = ets_class_from_arg(sch, arg); + struct ets_class *cl = ets_class_from_arg(arg); struct ets_sched *q = qdisc_priv(sch); struct nlattr *nest; @@ -322,7 +319,7 @@ static int ets_class_dump(struct Qdisc *sch, unsigned long arg, static int ets_class_dump_stats(struct Qdisc *sch, unsigned long arg, struct gnet_dump *d) { - struct ets_class *cl = ets_class_from_arg(sch, arg); + struct ets_class *cl = ets_class_from_arg(arg); struct Qdisc *cl_q = cl->qdisc; if (gnet_stats_copy_basic(d, NULL, &cl_q->bstats, true) < 0 ||