[PATCH 4.9 72/78] sch_tbf: fix two null pointer dereferences on init failure

From: Greg Kroah-Hartman
Date: Thu Sep 13 2018 - 09:40:02 EST

4.9-stable review patch. If anyone has any objections, please let me know.

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

From: Nikolay Aleksandrov <nikolay@xxxxxxxxxxxxxxxxxxx>

commit c2d6511e6a4f1f3673d711569c00c3849549e9b0 upstream.

sch_tbf calls qdisc_watchdog_cancel() in both its ->reset and ->destroy
callbacks but it may fail before the timer is initialized due to missing
options (either not supplied by user-space or set as a default qdisc),
also q->qdisc is used by ->reset and ->destroy so we need it initialized.

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

Crash log:
[ 959.160172] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
[ 959.160323] IP: qdisc_reset+0xa/0x5c
[ 959.160400] PGD 59cdb067
[ 959.160401] P4D 59cdb067
[ 959.160466] PUD 59ccb067
[ 959.160532] PMD 0
[ 959.160597]
[ 959.160706] Oops: 0000 [#1] SMP
[ 959.160778] Modules linked in: sch_tbf sch_sfb sch_prio sch_netem
[ 959.160891] CPU: 2 PID: 1562 Comm: ip Not tainted 4.13.0-rc6+ #62
[ 959.160998] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014
[ 959.161157] task: ffff880059c9a700 task.stack: ffff8800376d0000
[ 959.161263] RIP: 0010:qdisc_reset+0xa/0x5c
[ 959.161347] RSP: 0018:ffff8800376d3610 EFLAGS: 00010286
[ 959.161531] RAX: ffffffffa001b1dd RBX: ffff8800373a2800 RCX: 0000000000000000
[ 959.161733] RDX: ffffffff8215f160 RSI: ffffffff8215f160 RDI: 0000000000000000
[ 959.161939] RBP: ffff8800376d3618 R08: 00000000014080c0 R09: 00000000ffffffff
[ 959.162141] R10: ffff8800376d3578 R11: 0000000000000020 R12: ffffffffa001d2c0
[ 959.162343] R13: ffff880037538000 R14: 00000000ffffffff R15: 0000000000000001
[ 959.162546] FS: 00007fcc5126b740(0000) GS:ffff88005d900000(0000) knlGS:0000000000000000
[ 959.162844] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 959.163030] CR2: 0000000000000018 CR3: 000000005abc4000 CR4: 00000000000406e0
[ 959.163233] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 959.163436] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 959.163638] Call Trace:
[ 959.163788] tbf_reset+0x19/0x64 [sch_tbf]
[ 959.163957] qdisc_destroy+0x8b/0xe5
[ 959.164119] qdisc_create_dflt+0x86/0x94
[ 959.164284] ? dev_activate+0x129/0x129
[ 959.164449] attach_one_default_qdisc+0x36/0x63
[ 959.164623] netdev_for_each_tx_queue+0x3d/0x48
[ 959.164795] dev_activate+0x4b/0x129
[ 959.164957] __dev_open+0xe7/0x104
[ 959.165118] __dev_change_flags+0xc6/0x15c
[ 959.165287] dev_change_flags+0x25/0x59
[ 959.165451] do_setlink+0x30c/0xb3f
[ 959.165613] ? check_chain_key+0xb0/0xfd
[ 959.165782] rtnl_newlink+0x3a4/0x729
[ 959.165947] ? rtnl_newlink+0x117/0x729
[ 959.166121] ? ns_capable_common+0xd/0xb1
[ 959.166288] ? ns_capable+0x13/0x15
[ 959.166450] rtnetlink_rcv_msg+0x188/0x197
[ 959.166617] ? rcu_read_unlock+0x3e/0x5f
[ 959.166783] ? rtnl_newlink+0x729/0x729
[ 959.166948] netlink_rcv_skb+0x6c/0xce
[ 959.167113] rtnetlink_rcv+0x23/0x2a
[ 959.167273] netlink_unicast+0x103/0x181
[ 959.167439] netlink_sendmsg+0x326/0x337
[ 959.167607] sock_sendmsg_nosec+0x14/0x3f
[ 959.167772] sock_sendmsg+0x29/0x2e
[ 959.167932] ___sys_sendmsg+0x209/0x28b
[ 959.168098] ? do_raw_spin_unlock+0xcd/0xf8
[ 959.168267] ? _raw_spin_unlock+0x27/0x31
[ 959.168432] ? __handle_mm_fault+0x651/0xdb1
[ 959.168602] ? check_chain_key+0xb0/0xfd
[ 959.168773] __sys_sendmsg+0x45/0x63
[ 959.168934] ? __sys_sendmsg+0x45/0x63
[ 959.169100] SyS_sendmsg+0x19/0x1b
[ 959.169260] entry_SYSCALL_64_fastpath+0x23/0xc2
[ 959.169432] RIP: 0033:0x7fcc5097e690
[ 959.169592] RSP: 002b:00007ffd0d5c7b48 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[ 959.169887] RAX: ffffffffffffffda RBX: ffffffff810d278c RCX: 00007fcc5097e690
[ 959.170089] RDX: 0000000000000000 RSI: 00007ffd0d5c7b90 RDI: 0000000000000003
[ 959.170292] RBP: ffff8800376d3f98 R08: 0000000000000001 R09: 0000000000000003
[ 959.170494] R10: 00007ffd0d5c7910 R11: 0000000000000246 R12: 0000000000000006
[ 959.170697] R13: 000000000066f1a0 R14: 00007ffd0d5cfc40 R15: 0000000000000000
[ 959.170900] ? trace_hardirqs_off_caller+0xa7/0xcf
[ 959.171076] Code: 00 41 c7 84 24 14 01 00 00 00 00 00 00 41 c7 84 24
98 00 00 00 00 00 00 00 41 5c 41 5d 41 5e 5d c3 66 66 66 66 90 55 48 89
e5 53 <48> 8b 47 18 48 89 fb 48 8b 40 48 48 85 c0 74 02 ff d0 48 8b bb
[ 959.171637] RIP: qdisc_reset+0xa/0x5c RSP: ffff8800376d3610
[ 959.171821] CR2: 0000000000000018

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@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Amit Pundir <amit.pundir@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/sched/sch_tbf.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/net/sched/sch_tbf.c
+++ b/net/sched/sch_tbf.c
@@ -423,12 +423,13 @@ static int tbf_init(struct Qdisc *sch, s
{
struct tbf_sched_data *q = qdisc_priv(sch);

+ qdisc_watchdog_init(&q->watchdog, sch);
+ q->qdisc = &noop_qdisc;
+
if (opt == NULL)
return -EINVAL;

q->t_c = ktime_get_ns();
- qdisc_watchdog_init(&q->watchdog, sch);
- q->qdisc = &noop_qdisc;

return tbf_change(sch, opt);
}