netdev - [PATCH net] net/sched: taprio: fix duration_to

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Message-ID: <20240523134549.160106-1-edumazet@google.com>
Date: Thu, 23 May 2024 13:45:49 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang <xiyou.wangcong@...il.com>, 
	Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>, syzbot <syzkaller@...glegroups.com>, 
	Vladimir Oltean <vladimir.oltean@....com>, Vinicius Costa Gomes <vinicius.gomes@...el.com>
Subject: [PATCH net] net/sched: taprio: fix duration_to_length()

duration_to_length() is incorrectly using div_u64()
instead of div64_u64().

syzbot reported:

Oops: divide error: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 1 PID: 15391 Comm: syz-executor.0 Not tainted 6.9.0-syzkaller-08544-g4b377b4868ef #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
 RIP: 0010:div_u64_rem include/linux/math64.h:29 [inline]
 RIP: 0010:div_u64 include/linux/math64.h:130 [inline]
 RIP: 0010:duration_to_length net/sched/sch_taprio.c:259 [inline]
 RIP: 0010:taprio_update_queue_max_sdu+0x287/0x870 net/sched/sch_taprio.c:288
Code: be 08 00 00 00 e8 99 5b 6a f8 48 89 d8 48 c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 13 59 6a f8 48 8b 03 89 c1 48 89 e8 31 d2 <48> f7 f1 48 89 c5 48 83 7c 24 50 00 4c 8b 74 24 30 74 47 e8 c1 19
RSP: 0018:ffffc9000506eb38 EFLAGS: 00010246
RAX: 0000000000001f40 RBX: ffff88802f3562e0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffff88802f3562e0
RBP: 0000000000001f40 R08: ffff88802f3562e7 R09: 1ffff11005e6ac5c
R10: dffffc0000000000 R11: ffffed1005e6ac5d R12: 00000000ffffffff
R13: dffffc0000000000 R14: ffff88801ef59400 R15: 00000000003f0008
FS:  00007fee340bf6c0(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2c524000 CR3: 0000000024a52000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  taprio_change+0x2dce/0x42d0 net/sched/sch_taprio.c:1911
  taprio_init+0x9da/0xc80 net/sched/sch_taprio.c:2112
  qdisc_create+0x9d4/0x11a0 net/sched/sch_api.c:1355
  tc_modify_qdisc+0xa26/0x1e40 net/sched/sch_api.c:1777
  rtnetlink_rcv_msg+0x89b/0x10d0 net/core/rtnetlink.c:6595
  netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2564
  netlink_unicast_kernel net/netlink/af_netlink.c:1335 [inline]
  netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1361
  netlink_sendmsg+0x8e1/0xcb0 net/netlink/af_netlink.c:1905
  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_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fee3327cee9

Fixes: fed87cc6718a ("net/sched: taprio: automatically calculate queueMaxSDU based on TC gate durations")
Reported-by: syzbot <syzkaller@...glegroups.com>
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Vladimir Oltean <vladimir.oltean@....com>
Cc: Vinicius Costa Gomes <vinicius.gomes@...el.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 1ab17e8a72605385280fad9b7f656a6771236acc..827fb81fc63a098304bad198fadd4aed55d1fec4 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -256,7 +256,8 @@ static int length_to_duration(struct taprio_sched *q, int len)
 
 static int duration_to_length(struct taprio_sched *q, u64 duration)
 {
-	return div_u64(duration * PSEC_PER_NSEC, atomic64_read(&q->picos_per_byte));
+	return div64_u64(duration * PSEC_PER_NSEC,
+			 atomic64_read(&q->picos_per_byte));
 }
 
 /* Sets sched->max_sdu[] and sched->max_frm_len[] to the minimum between the
-- 
2.45.1.288.g0e0cd299f1-goog