net: sched: validate stab values

iproute2 package is well behaved, but malicious user space can
provide illegal shift values and trigger UBSAN reports.

Add stab parameter to red_check_params() to validate user input.

syzbot reported:

UBSAN: shift-out-of-bounds in ./include/net/red.h:312:18
shift exponent 111 is too large for 64-bit type 'long unsigned int'
CPU: 1 PID: 14662 Comm: syz-executor.3 Not tainted 5.12.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x141/0x1d7 lib/dump_stack.c:120
 ubsan_epilogue+0xb/0x5a lib/ubsan.c:148
 __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x181 lib/ubsan.c:327
 red_calc_qavg_from_idle_time include/net/red.h:312 [inline]
 red_calc_qavg include/net/red.h:353 [inline]
 choke_enqueue.cold+0x18/0x3dd net/sched/sch_choke.c:221
 __dev_xmit_skb net/core/dev.c:3837 [inline]
 __dev_queue_xmit+0x1943/0x2e00 net/core/dev.c:4150
 neigh_hh_output include/net/neighbour.h:499 [inline]
 neigh_output include/net/neighbour.h:508 [inline]
 ip6_finish_output2+0x911/0x1700 net/ipv6/ip6_output.c:117
 __ip6_finish_output net/ipv6/ip6_output.c:182 [inline]
 __ip6_finish_output+0x4c1/0xe10 net/ipv6/ip6_output.c:161
 ip6_finish_output+0x35/0x200 net/ipv6/ip6_output.c:192
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip6_output+0x1e4/0x530 net/ipv6/ip6_output.c:215
 dst_output include/net/dst.h:448 [inline]
 NF_HOOK include/linux/netfilter.h:301 [inline]
 NF_HOOK include/linux/netfilter.h:295 [inline]
 ip6_xmit+0x127e/0x1eb0 net/ipv6/ip6_output.c:320
 inet6_csk_xmit+0x358/0x630 net/ipv6/inet6_connection_sock.c:135
 dccp_transmit_skb+0x973/0x12c0 net/dccp/output.c:138
 dccp_send_reset+0x21b/0x2b0 net/dccp/output.c:535
 dccp_finish_passive_close net/dccp/proto.c:123 [inline]
 dccp_finish_passive_close+0xed/0x140 net/dccp/proto.c:118
 dccp_terminate_connection net/dccp/proto.c:958 [inline]
 dccp_close+0xb3c/0xe60 net/dccp/proto.c:1028
 inet_release+0x12e/0x280 net/ipv4/af_inet.c:431
 inet6_release+0x4c/0x70 net/ipv6/af_inet6.c:478
 __sock_release+0xcd/0x280 net/socket.c:599
 sock_close+0x18/0x20 net/socket.c:1258
 __fput+0x288/0x920 fs/file_table.c:280
 task_work_run+0xdd/0x1a0 kernel/task_work.c:140
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]

Fixes: 8afa10cbe2 ("net_sched: red: Avoid illegal values")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/red.h

@@ -168,7 +168,8 @@ static inline void red_set_vars(struct red_vars *v)
 	v->qcount	= -1;
 }
 
-static inline bool red_check_params(u32 qth_min, u32 qth_max, u8 Wlog, u8 Scell_log)
+static inline bool red_check_params(u32 qth_min, u32 qth_max, u8 Wlog,
+				    u8 Scell_log, u8 *stab)
 {
 	if (fls(qth_min) + Wlog > 32)
 		return false;
@@ -178,6 +179,13 @@ static inline bool red_check_params(u32 qth_min, u32 qth_max, u8 Wlog, u8 Scell_
 		return false;
 	if (qth_max < qth_min)
 		return false;
+	if (stab) {
+		int i;
+
+		for (i = 0; i < RED_STAB_SIZE; i++)
+			if (stab[i] >= 32)
+				return false;
+	}
 	return true;
 }
 

net/sched/sch_choke.c

@@ -345,6 +345,7 @@ static int choke_change(struct Qdisc *sch, struct nlattr *opt,
 	struct sk_buff **old = NULL;
 	unsigned int mask;
 	u32 max_P;
+	u8 *stab;
 
 	if (opt == NULL)
 		return -EINVAL;
@@ -361,8 +362,8 @@ static int choke_change(struct Qdisc *sch, struct nlattr *opt,
 	max_P = tb[TCA_CHOKE_MAX_P] ? nla_get_u32(tb[TCA_CHOKE_MAX_P]) : 0;
 
 	ctl = nla_data(tb[TCA_CHOKE_PARMS]);
-
-	if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog, ctl->Scell_log))
+	stab = nla_data(tb[TCA_CHOKE_STAB]);
+	if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog, ctl->Scell_log, stab))
 		return -EINVAL;
 
 	if (ctl->limit > CHOKE_MAX_QUEUE)
@@ -412,7 +413,7 @@ static int choke_change(struct Qdisc *sch, struct nlattr *opt,
 
 	red_set_parms(&q->parms, ctl->qth_min, ctl->qth_max, ctl->Wlog,
 		      ctl->Plog, ctl->Scell_log,
-		      nla_data(tb[TCA_CHOKE_STAB]),
+		      stab,
 		      max_P);
 	red_set_vars(&q->vars);
 

net/sched/sch_gred.c

@@ -480,7 +480,7 @@ static inline int gred_change_vq(struct Qdisc *sch, int dp,
 	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, ctl->Scell_log)) {
+	if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog, ctl->Scell_log, stab)) {
 		NL_SET_ERR_MSG_MOD(extack, "invalid RED parameters");
 		return -EINVAL;
 	}

net/sched/sch_red.c

@@ -242,6 +242,7 @@ static int __red_change(struct Qdisc *sch, struct nlattr **tb,
 	unsigned char flags;
 	int err;
 	u32 max_P;
+	u8 *stab;
 
 	if (tb[TCA_RED_PARMS] == NULL ||
 	    tb[TCA_RED_STAB] == NULL)
@@ -250,7 +251,9 @@ static int __red_change(struct Qdisc *sch, struct nlattr **tb,
 	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, ctl->Scell_log))
+	stab = nla_data(tb[TCA_RED_STAB]);
+	if (!red_check_params(ctl->qth_min, ctl->qth_max, ctl->Wlog,
+			      ctl->Scell_log, stab))
 		return -EINVAL;
 
 	err = red_get_flags(ctl->flags, TC_RED_HISTORIC_FLAGS,
@@ -288,7 +291,7 @@ static int __red_change(struct Qdisc *sch, struct nlattr **tb,
 	red_set_parms(&q->parms,
 		      ctl->qth_min, ctl->qth_max, ctl->Wlog,
 		      ctl->Plog, ctl->Scell_log,
-		      nla_data(tb[TCA_RED_STAB]),
+		      stab,
 		      max_P);
 	red_set_vars(&q->vars);
 

net/sched/sch_sfq.c

@@ -647,7 +647,7 @@ static int sfq_change(struct Qdisc *sch, struct nlattr *opt)
 	}
 
 	if (ctl_v1 && !red_check_params(ctl_v1->qth_min, ctl_v1->qth_max,
-					ctl_v1->Wlog, ctl_v1->Scell_log))
+					ctl_v1->Wlog, ctl_v1->Scell_log, NULL))
 		return -EINVAL;
 	if (ctl_v1 && ctl_v1->qth_min) {
 		p = kmalloc(sizeof(*p), GFP_KERNEL);