dafabb6590
In the datapath, the ip6gre_tunnel_lookup() is used and it internally uses
fallback tunnel device pointer, which is fb_tunnel_dev.
This pointer variable should be set to NULL when a fb interface is deleted.
But there is no routine to set fb_tunnel_dev pointer to NULL.
So, this pointer will be still used after interface is deleted and
it eventually results in the use-after-free problem.
Test commands:
ip netns add A
ip netns add B
ip link add eth0 type veth peer name eth1
ip link set eth0 netns A
ip link set eth1 netns B
ip netns exec A ip link set lo up
ip netns exec A ip link set eth0 up
ip netns exec A ip link add ip6gre1 type ip6gre local fc:0::1 \
remote fc:0::2
ip netns exec A ip -6 a a fc💯:1/64 dev ip6gre1
ip netns exec A ip link set ip6gre1 up
ip netns exec A ip -6 a a fc:0::1/64 dev eth0
ip netns exec A ip link set ip6gre0 up
ip netns exec B ip link set lo up
ip netns exec B ip link set eth1 up
ip netns exec B ip link add ip6gre1 type ip6gre local fc:0::2 \
remote fc:0::1
ip netns exec B ip -6 a a fc💯:2/64 dev ip6gre1
ip netns exec B ip link set ip6gre1 up
ip netns exec B ip -6 a a fc:0::2/64 dev eth1
ip netns exec B ip link set ip6gre0 up
ip netns exec A ping fc💯:2 -s 60000 &
ip netns del B
Splat looks like:
[ 73.087285][ C1] BUG: KASAN: use-after-free in ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre]
[ 73.088361][ C1] Read of size 4 at addr ffff888040559218 by task ping/1429
[ 73.089317][ C1]
[ 73.089638][ C1] CPU: 1 PID: 1429 Comm: ping Not tainted 5.7.0+ #602
[ 73.090531][ C1] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[ 73.091725][ C1] Call Trace:
[ 73.092160][ C1] <IRQ>
[ 73.092556][ C1] dump_stack+0x96/0xdb
[ 73.093122][ C1] print_address_description.constprop.6+0x2cc/0x450
[ 73.094016][ C1] ? ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre]
[ 73.094894][ C1] ? ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre]
[ 73.095767][ C1] ? ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre]
[ 73.096619][ C1] kasan_report+0x154/0x190
[ 73.097209][ C1] ? ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre]
[ 73.097989][ C1] ip6gre_tunnel_lookup+0x1064/0x13f0 [ip6_gre]
[ 73.098750][ C1] ? gre_del_protocol+0x60/0x60 [gre]
[ 73.099500][ C1] gre_rcv+0x1c5/0x1450 [ip6_gre]
[ 73.100199][ C1] ? ip6gre_header+0xf00/0xf00 [ip6_gre]
[ 73.100985][ C1] ? rcu_read_lock_sched_held+0xc0/0xc0
[ 73.101830][ C1] ? ip6_input_finish+0x5/0xf0
[ 73.102483][ C1] ip6_protocol_deliver_rcu+0xcbb/0x1510
[ 73.103296][ C1] ip6_input_finish+0x5b/0xf0
[ 73.103920][ C1] ip6_input+0xcd/0x2c0
[ 73.104473][ C1] ? ip6_input_finish+0xf0/0xf0
[ 73.105115][ C1] ? rcu_read_lock_held+0x90/0xa0
[ 73.105783][ C1] ? rcu_read_lock_sched_held+0xc0/0xc0
[ 73.106548][ C1] ipv6_rcv+0x1f1/0x300
[ ... ]
Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Fixes: c12b395a46 ("gre: Support GRE over IPv6")
Signed-off-by: Taehee Yoo <ap420073@gmail.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.