[PATCH net] net/sched: taprio: proper TCA_TAPRIO_TC_ENTRY_INDEX check

[Eric Dumazet <edumazet@google.com>]

taprio_parse_tc_entry() is not correctly checking
TCA_TAPRIO_TC_ENTRY_INDEX attribute:

	int tc; // Signed value

	tc = nla_get_u32(tb[TCA_TAPRIO_TC_ENTRY_INDEX]);
	if (tc >= TC_QOPT_MAX_QUEUE) {
		NL_SET_ERR_MSG_MOD(extack, "TC entry index out of range");
		return -ERANGE;
	}

syzbot reported that it could fed arbitary negative values:

UBSAN: shift-out-of-bounds in net/sched/sch_taprio.c:1722:18
shift exponent -2147418108 is negative
CPU: 0 PID: 5066 Comm: syz-executor367 Not tainted 6.8.0-rc7-syzkaller-00136-gc8a5c731fd12 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
Call Trace:
 <TASK>
  __dump_stack lib/dump_stack.c:88 [inline]
  dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
  ubsan_epilogue lib/ubsan.c:217 [inline]
  __ubsan_handle_shift_out_of_bounds+0x3c7/0x420 lib/ubsan.c:386
  taprio_parse_tc_entry net/sched/sch_taprio.c:1722 [inline]
  taprio_parse_tc_entries net/sched/sch_taprio.c:1768 [inline]
  taprio_change+0xb87/0x57d0 net/sched/sch_taprio.c:1877
  taprio_init+0x9da/0xc80 net/sched/sch_taprio.c:2134
  qdisc_create+0x9d4/0x1190 net/sched/sch_api.c:1355
  tc_modify_qdisc+0xa26/0x1e40 net/sched/sch_api.c:1776
  rtnetlink_rcv_msg+0x885/0x1040 net/core/rtnetlink.c:6617
  netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2543
  netlink_unicast_kernel net/netlink/af_netlink.c:1341 [inline]
  netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1367
  netlink_sendmsg+0xa3b/0xd70 net/netlink/af_netlink.c:1908
  sock_sendmsg_nosec net/socket.c:730 [inline]
  __sock_sendmsg+0x221/0x270 net/socket.c:745
  ____sys_sendmsg+0x525/0x7d0 net/socket.c:2584
  ___sys_sendmsg net/socket.c:2638 [inline]
  __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2667
 do_syscall_64+0xf9/0x240
 entry_SYSCALL_64_after_hwframe+0x6f/0x77
RIP: 0033:0x7f1b2dea3759
Code: 48 83 c4 28 c3 e8 d7 19 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd4de452f8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f1b2def0390 RCX: 00007f1b2dea3759
RDX: 0000000000000000 RSI: 00000000200007c0 RDI: 0000000000000004
RBP: 0000000000000003 R08: 0000555500000000 R09: 0000555500000000
R10: 0000555500000000 R11: 0000000000000246 R12: 00007ffd4de45340
R13: 00007ffd4de45310 R14: 0000000000000001 R15: 00007ffd4de45340

Fixes: a54fc09e4cba ("net/sched: taprio: allow user input of per-tc max SDU")
Reported-and-tested-by: syzbot+a340daa06412d6028918@syzkaller.appspotmail.com
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 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 31a8252bd09c9111090f0147df6deb0ad81577af..ad99409c6325e179319f8ec4053582417a978817 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1008,7 +1008,8 @@ static const struct nla_policy entry_policy[TCA_TAPRIO_SCHED_ENTRY_MAX + 1] = {
 };
 
 static const struct nla_policy taprio_tc_policy[TCA_TAPRIO_TC_ENTRY_MAX + 1] = {
-	[TCA_TAPRIO_TC_ENTRY_INDEX]	   = { .type = NLA_U32 },
+	[TCA_TAPRIO_TC_ENTRY_INDEX]	   = NLA_POLICY_MAX(NLA_U32,
+							    TC_QOPT_MAX_QUEUE),
 	[TCA_TAPRIO_TC_ENTRY_MAX_SDU]	   = { .type = NLA_U32 },
 	[TCA_TAPRIO_TC_ENTRY_FP]	   = NLA_POLICY_RANGE(NLA_U32,
 							      TC_FP_EXPRESS,
-- 
2.44.0.278.ge034bb2e1d-goog