CVE-2023-54251: In the Linux kernel, the following vulnerability has been resolved:  net/sched: taprio: Limit TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME to INT_MAX.  syzkaller found zero division error [0] in div_s64_rem() called from get_cycle_time_elapsed(), where sched->cycle_time is the divisor.  We have tests in parse_taprio_schedule() so that cycle_time will never be 0, and actually cycle_time is not 0 in get_cycle_time_elapsed().  The problem is that the types of divisor are different; cycle_time is s64, but the argument of div_s64_rem() is s32.  syzkaller fed this input and 0x100000000 is cast to s32 to be 0.    @TCA_TAPRIO_ATTR_SCHED_CYCLE_TIME={0xc, 0x8, 0x100000000}  We use s64 for cycle_time to cast it to ktime_t, so let's keep it and set max for cycle_time.  While at it, we prevent overflow in setup_txtime() and add another test in parse_taprio_schedule() to check if cycle_time overflows.  Also, we add a new tdc test case for this issue.  [0]: divide error: 0000 [#1] PREEMPT SMP KASAN NOPTI CPU: 1 PID: 103 Comm: kworker/1:3 Not tainted 6.5.0-rc1-00330-g60cc1f7d0605 #3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 Workqueue: ipv6_addrconf addrconf_dad_work RIP: 0010:div_s64_rem include/linux/math64.h:42 [inline] RIP: 0010:get_cycle_time_elapsed net/sched/sch_taprio.c:223 [inline] RIP: 0010:find_entry_to_transmit+0x252/0x7e0 net/sched/sch_taprio.c:344 Code: 3c 02 00 0f 85 5e 05 00 00 48 8b 4c 24 08 4d 8b bd 40 01 00 00 48 8b 7c 24 48 48 89 c8 4c 29 f8 48 63 f7 48 99 48 89 74 24 70 <48> f7 fe 48 29 d1 48 8d 04 0f 49 89 cc 48 89 44 24 20 49 8d 85 10 RSP: 0018:ffffc90000acf260 EFLAGS: 00010206 RAX: 177450e0347560cf RBX: 0000000000000000 RCX: 177450e0347560cf RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000100000000 RBP: 0000000000000056 R08: 0000000000000000 R09: ffffed10020a0934 R10: ffff8880105049a7 R11: ffff88806cf3a520 R12: ffff888010504800 R13: ffff88800c00d800 R14: ffff8880105049a0 R15: 0000000000000000 FS:  0000000000000000(0000) GS:ffff88806cf00000(0000) knlGS:0000000000000000 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f0edf84f0e8 CR3: 000000000d73c002 CR4: 0000000000770ee0 PKRU: 55555554 Call Trace:  <TASK>  get_packet_txtime net/sched/sch_taprio.c:508 [inline]  taprio_enqueue_one+0x900/0xff0 net/sched/sch_taprio.c:577  taprio_enqueue+0x378/0xae0 net/sched/sch_taprio.c:658  dev_qdisc_enqueue+0x46/0x170 net/core/dev.c:3732  __dev_xmit_skb net/core/dev.c:3821 [inline]  __dev_queue_xmit+0x1b2f/0x3000 net/core/dev.c:4169  dev_queue_xmit include/linux/netdevice.h:3088 [inline]  neigh_resolve_output net/core/neighbour.c:1552 [inline]  neigh_resolve_output+0x4a7/0x780 net/core/neighbour.c:1532  neigh_output include/net/neighbour.h:544 [inline]  ip6_finish_output2+0x924/0x17d0 net/ipv6/ip6_output.c:135  __ip6_finish_output+0x620/0xaa0 net/ipv6/ip6_output.c:196  ip6_finish_output net/ipv6/ip6_output.c:207 [inline]  NF_HOOK_COND include/linux/netfilter.h:292 [inline]  ip6_output+0x206/0x410 net/ipv6/ip6_output.c:228  dst_output include/net/dst.h:458 [inline]  NF_HOOK.constprop.0+0xea/0x260 include/linux/netfilter.h:303  ndisc_send_skb+0x872/0xe80 net/ipv6/ndisc.c:508  ndisc_send_ns+0xb5/0x130 net/ipv6/ndisc.c:666  addrconf_dad_work+0xc14/0x13f0 net/ipv6/addrconf.c:4175  process_one_work+0x92c/0x13a0 kernel/workqueue.c:2597  worker_thread+0x60f/0x1240 kernel/workqueue.c:2748  kthread+0x2fe/0x3f0 kernel/kthread.c:389  ret_from_fork+0x2c/0x50 arch/x86/entry/entry_64.S:308  </TASK> Modules linked in: