| Message ID | 20190502151318.1884-1-mcroce@redhat.com |
|---|---|
| State | Accepted |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] cls_cgroup: avoid panic when receiving a packet before filter set | expand |
From: Matteo Croce <mcroce@redhat.com> Date: Thu, 2 May 2019 17:13:18 +0200 > When a cgroup classifier is added, there is a small time interval in > which tp->root is NULL. If we receive a packet in this small time slice > a NULL pointer dereference will happen, leading to a kernel panic: ... > Suggested-by: Cong Wang <xiyou.wangcong@gmail.com> > Fixes: ed76f5edccc9 ("net: sched: protect filter_chain list with filter_chain_lock mutex") > Signed-off-by: Matteo Croce <mcroce@redhat.com> Applied, thanks.
diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c index 4c1567854f95..706a160142ea 100644 --- a/net/sched/cls_cgroup.c +++ b/net/sched/cls_cgroup.c @@ -32,6 +32,8 @@ static int cls_cgroup_classify(struct sk_buff *skb, const struct tcf_proto *tp, struct cls_cgroup_head *head = rcu_dereference_bh(tp->root); u32 classid = task_get_classid(skb); + if (unlikely(!head)) + return -1; if (!classid) return -1; if (!tcf_em_tree_match(skb, &head->ematches, NULL))
When a cgroup classifier is added, there is a small time interval in which tp->root is NULL. If we receive a packet in this small time slice a NULL pointer dereference will happen, leading to a kernel panic: # mkdir /sys/fs/cgroup/net_cls/0 # echo 0x100001 > /sys/fs/cgroup/net_cls/0/net_cls.classid # echo $$ >/sys/fs/cgroup/net_cls/0/tasks # ping -qfb 255.255.255.255 -I eth0 &>/dev/null & # tc qdisc add dev eth0 root handle 10: htb # while : ; do > tc filter add dev eth0 parent 10: protocol ip prio 10 handle 1: cgroup > tc filter delete dev eth0 > done Unable to handle kernel NULL pointer dereference at virtual address 0000000000000028 Mem abort info: ESR = 0x96000005 Exception class = DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 Data abort info: ISV = 0, ISS = 0x00000005 CM = 0, WnR = 0 user pgtable: 4k pages, 39-bit VAs, pgdp = 0000000098a7ff91 [0000000000000028] pgd=0000000000000000, pud=0000000000000000 Internal error: Oops: 96000005 [#1] SMP Modules linked in: sch_htb cls_cgroup algif_hash af_alg nls_iso8859_1 nls_cp437 vfat fat xhci_plat_hcd m25p80 spi_nor xhci_hcd mtd usbcore usb_common spi_orion sfp i2c_mv64xxx phy_generic mdio_i2c marvell10g i2c_core mvpp2 mvmdio phylink sbsa_gwdt ip_tables x_tables autofs4 Process ping (pid: 5421, stack limit = 0x00000000b20b1505) CPU: 3 PID: 5421 Comm: ping Not tainted 5.1.0-rc6 #31 Hardware name: Marvell 8040 MACCHIATOBin Double-shot (DT) pstate: 60000005 (nZCv daif -PAN -UAO) pc : cls_cgroup_classify+0x80/0xec [cls_cgroup] lr : cls_cgroup_classify+0x34/0xec [cls_cgroup] sp : ffffff8012e6b850 x29: ffffff8012e6b850 x28: ffffffc423dd3c00 x27: ffffff801093ebc0 x26: ffffffc425a85b00 x25: 0000000020000000 x24: 0000000000000000 x23: ffffff8012e6b910 x22: ffffffc428db4900 x21: ffffff8012e6b910 x20: 0000000000100001 x19: 0000000000000000 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000000 x13: 0000000000000000 x12: 000000000000001c x11: 0000000000000018 x10: ffffff8012e6b840 x9 : 0000000000003580 x8 : 000000000000009d x7 : 0000000000000002 x6 : ffffff8012e6b860 x5 : 000000007cd66ffe x4 : 000000009742a193 x3 : ffffff800865b4d8 x2 : ffffff8012e6b910 x1 : 0000000000000400 x0 : ffffffc42c38f300 Call trace: cls_cgroup_classify+0x80/0xec [cls_cgroup] tcf_classify+0x78/0x138 htb_enqueue+0x74/0x320 [sch_htb] __dev_queue_xmit+0x3e4/0x9d0 dev_queue_xmit+0x24/0x30 ip_finish_output2+0x2e4/0x4d0 ip_finish_output+0x1d8/0x270 ip_mc_output+0xa8/0x240 ip_local_out+0x58/0x68 ip_send_skb+0x2c/0x88 ip_push_pending_frames+0x44/0x50 raw_sendmsg+0x458/0x830 inet_sendmsg+0x54/0xe8 sock_sendmsg+0x34/0x50 __sys_sendto+0xd0/0x120 __arm64_sys_sendto+0x30/0x40 el0_svc_common.constprop.0+0x88/0xf8 el0_svc_handler+0x2c/0x38 el0_svc+0x8/0xc Code: 39496001 360002a1 b9425c14 34000274 (79405260) Suggested-by: Cong Wang <xiyou.wangcong@gmail.com> Fixes: ed76f5edccc9 ("net: sched: protect filter_chain list with filter_chain_lock mutex") Signed-off-by: Matteo Croce <mcroce@redhat.com> --- net/sched/cls_cgroup.c | 2 ++ 1 file changed, 2 insertions(+)