[PATCH -net] net: sched: prevent invalid Scell_log shift count

[PATCH -net] net: sched: prevent invalid Scell_log shift count

[Randy Dunlap]

Check Scell_log shift size in red_check_params() and modify all callers
of red_check_params() to pass Scell_log.

This prevents a shift out-of-bounds as detected by UBSAN:
  UBSAN: shift-out-of-bounds in ./include/net/red.h:252:22
  shift exponent 72 is too large for 32-bit type 'int'

Fixes: 8afa10cbe281 ("net_sched: red: Avoid illegal values")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: syzbot+97c5bd9cc81eca63d36e@syzkaller.appspotmail.com
Cc: Nogah Frankel <nogahf@mellanox.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: netdev@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
---
 include/net/red.h     |    4 +++-
 net/sched/sch_choke.c |    2 +-
 net/sched/sch_gred.c  |    2 +-
 net/sched/sch_red.c   |    2 +-
 net/sched/sch_sfq.c   |    2 +-
 5 files changed, 7 insertions(+), 5 deletions(-)

--- lnx-510.orig/include/net/red.h
+++ lnx-510/include/net/red.h
@@ -168,12 +168,14 @@ static inline void red_set_vars(struct r
 	v->qcount	= -1;
 }
 
-static inline bool red_check_params(u32 qth_min, u32 qth_max, u8 Wlog)
+static inline bool red_check_params(u32 qth_min, u32 qth_max, u8 Wlog, u8 Scell_log)
 {
 	if (fls(qth_min) + Wlog > 32)
 		return false;
 	if (fls(qth_max) + Wlog > 32)
 		return false;
+	if (Scell_log >= 32)
+		return false;
 	if (qth_max < qth_min)
 		return false;
 	return true;
--- lnx-510.orig/net/sched/sch_sfq.c
+++ lnx-510/net/sched/sch_sfq.c
@@ -647,7 +647,7 @@ static int sfq_change(struct Qdisc *sch,
 	}
 
 	if (ctl_v1 && !red_check_params(ctl_v1->qth_min, ctl_v1->qth_max,
-					ctl_v1->Wlog))
+					ctl_v1->Wlog, ctl_v1->Scell_log))
 		return -EINVAL;
 	if (ctl_v1 && ctl_v1->qth_min) {
 		p = kmalloc(sizeof(*p), GFP_KERNEL);
--- lnx-510.orig/net/sched/sch_choke.c
+++ lnx-510/net/sched/sch_choke.c
@@ -362,7 +362,7 @@ static int choke_change(struct Qdisc *sc
 
 	ctl = nla_data(tb[TCA_CHOKE_PARMS]);
 
-	if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog))
+	if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog, ctl->Scell_log))
 		return -EINVAL;
 
 	if (ctl->limit > CHOKE_MAX_QUEUE)
--- lnx-510.orig/net/sched/sch_gred.c
+++ lnx-510/net/sched/sch_gred.c
@@ -480,7 +480,7 @@ static inline int gred_change_vq(struct
 	struct gred_sched *table = qdisc_priv(sch);
 	struct gred_sched_data *q = table->tab[dp];
 
-	if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog)) {
+	if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog, ctl->Scell_log)) {
 		NL_SET_ERR_MSG_MOD(extack, "invalid RED parameters");
 		return -EINVAL;
 	}
--- lnx-510.orig/net/sched/sch_red.c
+++ lnx-510/net/sched/sch_red.c
@@ -250,7 +250,7 @@ static int __red_change(struct Qdisc *sc
 	max_P = tb[TCA_RED_MAX_P] ? nla_get_u32(tb[TCA_RED_MAX_P]) : 0;
 
 	ctl = nla_data(tb[TCA_RED_PARMS]);
-	if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog))
+	if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog, ctl->Scell_log))
 		return -EINVAL;
 
 	err = red_get_flags(ctl->flags, TC_RED_HISTORIC_FLAGS,

Re: [PATCH -net] net: sched: prevent invalid Scell_log shift count

[David Miller]

From: Randy Dunlap <rdunlap@infradead.org>
Date: Thu, 24 Dec 2020 22:23:44 -0800

> Check Scell_log shift size in red_check_params() and modify all callers
> of red_check_params() to pass Scell_log.
> 
> This prevents a shift out-of-bounds as detected by UBSAN:
>   UBSAN: shift-out-of-bounds in ./include/net/red.h:252:22
>   shift exponent 72 is too large for 32-bit type 'int'
> 
> Fixes: 8afa10cbe281 ("net_sched: red: Avoid illegal values")
> Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
> Reported-by: syzbot+97c5bd9cc81eca63d36e@syzkaller.appspotmail.com

Applied and queued up for -stable, thanks.