[PATCH 4.19 10/48] sch_choke: avoid potential panic in choke_reset()

Greg Kroah-Hartman
2020-05-13T09:46:02Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 8738c85c72b3108c9b9a369a39868ba5f8e10ae0 ]

If choke_init() could not allocate q->tab, we would crash later
in choke_reset().

BUG: KASAN: null-ptr-deref in memset include/linux/string.h:366 [inline]
BUG: KASAN: null-ptr-deref in choke_reset+0x208/0x340 net/sched/sch_choke.c:326
Write of size 8 at addr 0000000000000000 by task syz-executor822/7022

CPU: 1 PID: 7022 Comm: syz-executor822 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x188/0x20d lib/dump_stack.c:118
__kasan_report.cold+0x5/0x4d mm/kasan/report.c:515
kasan_report+0x33/0x50 mm/kasan/common.c:625
check_memory_region_inline mm/kasan/generic.c:187 [inline]
check_memory_region+0x141/0x190 mm/kasan/generic.c:193
memset+0x20/0x40 mm/kasan/common.c:85
memset include/linux/string.h:366 [inline]
choke_reset+0x208/0x340 net/sched/sch_choke.c:326
qdisc_reset+0x6b/0x520 net/sched/sch_generic.c:910
dev_deactivate_queue.constprop.0+0x13c/0x240 net/sched/sch_generic.c:1138
netdev_for_each_tx_queue include/linux/netdevice.h:2197 [inline]
dev_deactivate_many+0xe2/0xba0 net/sched/sch_generic.c:1195
dev_deactivate+0xf8/0x1c0 net/sched/sch_generic.c:1233
qdisc_graft+0xd25/0x1120 net/sched/sch_api.c:1051
tc_modify_qdisc+0xbab/0x1a00 net/sched/sch_api.c:1670
rtnetlink_rcv_msg+0x44e/0xad0 net/core/rtnetlink.c:5454
netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2469
netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
____sys_sendmsg+0x6bf/0x7e0 net/socket.c:2362
___sys_sendmsg+0x100/0x170 net/socket.c:2416
__sys_sendmsg+0xec/0x1b0 net/socket.c:2449
do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295

Fixes: 77e62da6e60c ("sch_choke: drop all packets in queue during reset")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sched/sch_choke.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/sched/sch_choke.c
+++ b/net/sched/sch_choke.c
@@ -327,7 +327,8 @@ static void choke_reset(struct Qdisc *sc

sch->q.qlen = 0;
sch->qstats.backlog = 0;
- memset(q->tab, 0, (q->tab_mask + 1) * sizeof(struct sk_buff *));
+ if (q->tab)
+ memset(q->tab, 0, (q->tab_mask + 1) * sizeof(struct sk_buff *));
q->head = q->tail = 0;
red_restart(&q->vars);
}