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Subject[PATCH 4.9 71/78] sch_netem: avoid null pointer deref on init failure
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>

commit 634576a1844dba15bc5e6fc61d72f37e13a21615 upstream.

netem can fail in ->init due to missing options (either not supplied by
user-space or used as a default qdisc) causing a timer->base null
pointer deref in its ->destroy() and ->reset() callbacks.

Reproduce:
$ sysctl net.core.default_qdisc=netem
$ ip l set ethX up

Crash log:
[ 1814.846943] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 1814.847181] IP: hrtimer_active+0x17/0x8a
[ 1814.847270] PGD 59c34067
[ 1814.847271] P4D 59c34067
[ 1814.847337] PUD 37374067
[ 1814.847403] PMD 0
[ 1814.847468]
[ 1814.847582] Oops: 0000 [#1] SMP
[ 1814.847655] Modules linked in: sch_netem(O) sch_fq_codel(O)
[ 1814.847761] CPU: 3 PID: 1573 Comm: ip Tainted: G O 4.13.0-rc6+ #62
[ 1814.847884] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
[ 1814.848043] task: ffff88003723a700 task.stack: ffff88005adc8000
[ 1814.848235] RIP: 0010:hrtimer_active+0x17/0x8a
[ 1814.848407] RSP: 0018:ffff88005adcb590 EFLAGS: 00010246
[ 1814.848590] RAX: 0000000000000000 RBX: ffff880058e359d8 RCX: 0000000000000000
[ 1814.848793] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff880058e359d8
[ 1814.848998] RBP: ffff88005adcb5b0 R08: 00000000014080c0 R09: 00000000ffffffff
[ 1814.849204] R10: ffff88005adcb660 R11: 0000000000000020 R12: 0000000000000000
[ 1814.849410] R13: ffff880058e359d8 R14: 00000000ffffffff R15: 0000000000000001
[ 1814.849616] FS: 00007f733bbca740(0000) GS:ffff88005d980000(0000) knlGS:0000000000000000
[ 1814.849919] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1814.850107] CR2: 0000000000000000 CR3: 0000000059f0d000 CR4: 00000000000406e0
[ 1814.850313] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 1814.850518] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 1814.850723] Call Trace:
[ 1814.850875] hrtimer_try_to_cancel+0x1a/0x93
[ 1814.851047] hrtimer_cancel+0x15/0x20
[ 1814.851211] qdisc_watchdog_cancel+0x12/0x14
[ 1814.851383] netem_reset+0xe6/0xed [sch_netem]
[ 1814.851561] qdisc_destroy+0x8b/0xe5
[ 1814.851723] qdisc_create_dflt+0x86/0x94
[ 1814.851890] ? dev_activate+0x129/0x129
[ 1814.852057] attach_one_default_qdisc+0x36/0x63
[ 1814.852232] netdev_for_each_tx_queue+0x3d/0x48
[ 1814.852406] dev_activate+0x4b/0x129
[ 1814.852569] __dev_open+0xe7/0x104
[ 1814.852730] __dev_change_flags+0xc6/0x15c
[ 1814.852899] dev_change_flags+0x25/0x59
[ 1814.853064] do_setlink+0x30c/0xb3f
[ 1814.853228] ? check_chain_key+0xb0/0xfd
[ 1814.853396] ? check_chain_key+0xb0/0xfd
[ 1814.853565] rtnl_newlink+0x3a4/0x729
[ 1814.853728] ? rtnl_newlink+0x117/0x729
[ 1814.853905] ? ns_capable_common+0xd/0xb1
[ 1814.854072] ? ns_capable+0x13/0x15
[ 1814.854234] rtnetlink_rcv_msg+0x188/0x197
[ 1814.854404] ? rcu_read_unlock+0x3e/0x5f
[ 1814.854572] ? rtnl_newlink+0x729/0x729
[ 1814.854737] netlink_rcv_skb+0x6c/0xce
[ 1814.854902] rtnetlink_rcv+0x23/0x2a
[ 1814.855064] netlink_unicast+0x103/0x181
[ 1814.855230] netlink_sendmsg+0x326/0x337
[ 1814.855398] sock_sendmsg_nosec+0x14/0x3f
[ 1814.855584] sock_sendmsg+0x29/0x2e
[ 1814.855747] ___sys_sendmsg+0x209/0x28b
[ 1814.855912] ? do_raw_spin_unlock+0xcd/0xf8
[ 1814.856082] ? _raw_spin_unlock+0x27/0x31
[ 1814.856251] ? __handle_mm_fault+0x651/0xdb1
[ 1814.856421] ? check_chain_key+0xb0/0xfd
[ 1814.856592] __sys_sendmsg+0x45/0x63
[ 1814.856755] ? __sys_sendmsg+0x45/0x63
[ 1814.856923] SyS_sendmsg+0x19/0x1b
[ 1814.857083] entry_SYSCALL_64_fastpath+0x23/0xc2
[ 1814.857256] RIP: 0033:0x7f733b2dd690
[ 1814.857419] RSP: 002b:00007ffe1d3387d8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[ 1814.858238] RAX: ffffffffffffffda RBX: ffffffff810d278c RCX: 00007f733b2dd690
[ 1814.858445] RDX: 0000000000000000 RSI: 00007ffe1d338820 RDI: 0000000000000003
[ 1814.858651] RBP: ffff88005adcbf98 R08: 0000000000000001 R09: 0000000000000003
[ 1814.858856] R10: 00007ffe1d3385a0 R11: 0000000000000246 R12: 0000000000000002
[ 1814.859060] R13: 000000000066f1a0 R14: 00007ffe1d3408d0 R15: 0000000000000000
[ 1814.859267] ? trace_hardirqs_off_caller+0xa7/0xcf
[ 1814.859446] Code: 10 55 48 89 c7 48 89 e5 e8 45 a1 fb ff 31 c0 5d c3
31 c0 c3 66 66 66 66 90 55 48 89 e5 41 56 41 55 41 54 53 49 89 fd 49 8b
45 30 <4c> 8b 20 41 8b 5c 24 38 31 c9 31 d2 48 c7 c7 50 8e 1d 82 41 89
[ 1814.860022] RIP: hrtimer_active+0x17/0x8a RSP: ffff88005adcb590
[ 1814.860214] CR2: 0000000000000000

Fixes: 87b60cfacf9f ("net_sched: fix error recovery at qdisc creation")
Fixes: 0fbbeb1ba43b ("[PKT_SCHED]: Fix missing qdisc_destroy() in qdisc_create_dflt()")
Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/sched/sch_netem.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -937,11 +937,11 @@ static int netem_init(struct Qdisc *sch,
struct netem_sched_data *q = qdisc_priv(sch);
int ret;

+ qdisc_watchdog_init(&q->watchdog, sch);
+
if (!opt)
return -EINVAL;

- qdisc_watchdog_init(&q->watchdog, sch);
-
q->loss_model = CLG_RANDOM;
ret = netem_change(sch, opt);
if (ret)

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