[PATCH 5.3 140/166] sch_cbq: validate TCA_CBQ_WRROPT to avoid crash

Greg Kroah-Hartman
2019-10-06T17:47:14Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit e9789c7cc182484fc031fd88097eb14cb26c4596 ]

syzbot reported a crash in cbq_normalize_quanta() caused
by an out of range cl->priority.

iproute2 enforces this check, but malicious users do not.

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN PTI
Modules linked in:
CPU: 1 PID: 26447 Comm: syz-executor.1 Not tainted 5.3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:cbq_normalize_quanta.part.0+0x1fd/0x430 net/sched/sch_cbq.c:902
RSP: 0018:ffff8801a5c333b0 EFLAGS: 00010206
RAX: 0000000020000003 RBX: 00000000fffffff8 RCX: ffffc9000712f000
RDX: 00000000000043bf RSI: ffffffff83be8962 RDI: 0000000100000018
RBP: ffff8801a5c33420 R08: 000000000000003a R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 00000000000002ef
R13: ffff88018da95188 R14: dffffc0000000000 R15: 0000000000000015
FS: 00007f37d26b1700(0000) GS:ffff8801dad00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004c7cec CR3: 00000001bcd0a006 CR4: 00000000001626f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
[<ffffffff83be9d57>] cbq_normalize_quanta include/net/pkt_sched.h:27 [inline]
[<ffffffff83be9d57>] cbq_addprio net/sched/sch_cbq.c:1097 [inline]
[<ffffffff83be9d57>] cbq_set_wrr+0x2d7/0x450 net/sched/sch_cbq.c:1115
[<ffffffff83bee8a7>] cbq_change_class+0x987/0x225b net/sched/sch_cbq.c:1537
[<ffffffff83b96985>] tc_ctl_tclass+0x555/0xcd0 net/sched/sch_api.c:2329
[<ffffffff83a84655>] rtnetlink_rcv_msg+0x485/0xc10 net/core/rtnetlink.c:5248
[<ffffffff83cadf0a>] netlink_rcv_skb+0x17a/0x460 net/netlink/af_netlink.c:2510
[<ffffffff83a7db6d>] rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:5266
[<ffffffff83cac2c6>] netlink_unicast_kernel net/netlink/af_netlink.c:1324 [inline]
[<ffffffff83cac2c6>] netlink_unicast+0x536/0x720 net/netlink/af_netlink.c:1350
[<ffffffff83cacd4a>] netlink_sendmsg+0x89a/0xd50 net/netlink/af_netlink.c:1939
[<ffffffff8399d46e>] sock_sendmsg_nosec net/socket.c:673 [inline]
[<ffffffff8399d46e>] sock_sendmsg+0x12e/0x170 net/socket.c:684
[<ffffffff8399f1fd>] ___sys_sendmsg+0x81d/0x960 net/socket.c:2359
[<ffffffff839a2d05>] __sys_sendmsg+0x105/0x1d0 net/socket.c:2397
[<ffffffff839a2df9>] SYSC_sendmsg net/socket.c:2406 [inline]
[<ffffffff839a2df9>] SyS_sendmsg+0x29/0x30 net/socket.c:2404
[<ffffffff8101ccc8>] do_syscall_64+0x528/0x770 arch/x86/entry/common.c:305
[<ffffffff84400091>] entry_SYSCALL_64_after_hwframe+0x42/0xb7

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sched/sch_cbq.c | 43 +++++++++++++++++++++++++++++--------------
1 file changed, 29 insertions(+), 14 deletions(-)

--- a/net/sched/sch_cbq.c
+++ b/net/sched/sch_cbq.c
@@ -1127,6 +1127,33 @@ static const struct nla_policy cbq_polic
[TCA_CBQ_POLICE] = { .len = sizeof(struct tc_cbq_police) },
};

+static int cbq_opt_parse(struct nlattr *tb[TCA_CBQ_MAX + 1],
+ struct nlattr *opt,
+ struct netlink_ext_ack *extack)
+{
+ int err;
+
+ if (!opt) {
+ NL_SET_ERR_MSG(extack, "CBQ options are required for this operation");
+ return -EINVAL;
+ }
+
+ err = nla_parse_nested_deprecated(tb, TCA_CBQ_MAX, opt,
+ cbq_policy, extack);
+ if (err < 0)
+ return err;
+
+ if (tb[TCA_CBQ_WRROPT]) {
+ const struct tc_cbq_wrropt *wrr = nla_data(tb[TCA_CBQ_WRROPT]);
+
+ if (wrr->priority > TC_CBQ_MAXPRIO) {
+ NL_SET_ERR_MSG(extack, "priority is bigger than TC_CBQ_MAXPRIO");
+ err = -EINVAL;
+ }
+ }
+ return err;
+}
+
static int cbq_init(struct Qdisc *sch, struct nlattr *opt,
struct netlink_ext_ack *extack)
{
@@ -1139,13 +1166,7 @@ static int cbq_init(struct Qdisc *sch, s
hrtimer_init(&q->delay_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
q->delay_timer.function = cbq_undelay;

- if (!opt) {
- NL_SET_ERR_MSG(extack, "CBQ options are required for this operation");
- return -EINVAL;
- }
-
- err = nla_parse_nested_deprecated(tb, TCA_CBQ_MAX, opt, cbq_policy,
- extack);
+ err = cbq_opt_parse(tb, opt, extack);
if (err < 0)
return err;

@@ -1464,13 +1485,7 @@ cbq_change_class(struct Qdisc *sch, u32
struct cbq_class *parent;
struct qdisc_rate_table *rtab = NULL;

- if (!opt) {
- NL_SET_ERR_MSG(extack, "Mandatory qdisc options missing");
- return -EINVAL;
- }
-
- err = nla_parse_nested_deprecated(tb, TCA_CBQ_MAX, opt, cbq_policy,
- extack);
+ err = cbq_opt_parse(tb, opt, extack);
if (err < 0)
return err;