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594725db0c
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)
Fixes: ed76f5edcc ("net: sched: protect filter_chain list with filter_chain_lock mutex")
Suggested-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.