102210f766
rmnet_get_port() internally calls rcu_dereference_rtnl(),
which checks RTNL.
But rmnet_get_port() could be called by packet path.
The packet path is not protected by RTNL.
So, the suspicious RCU usage problem occurs.
Test commands:
modprobe rmnet
ip netns add nst
ip link add veth0 type veth peer name veth1
ip link set veth1 netns nst
ip link add rmnet0 link veth0 type rmnet mux_id 1
ip netns exec nst ip link add rmnet1 link veth1 type rmnet mux_id 1
ip netns exec nst ip link set veth1 up
ip netns exec nst ip link set rmnet1 up
ip netns exec nst ip a a 192.168.100.2/24 dev rmnet1
ip link set veth0 up
ip link set rmnet0 up
ip a a 192.168.100.1/24 dev rmnet0
ping 192.168.100.2
Splat looks like:
[ 146.630958][ T1174] WARNING: suspicious RCU usage
[ 146.631735][ T1174] 5.6.0-rc1+ #447 Not tainted
[ 146.632387][ T1174] -----------------------------
[ 146.633151][ T1174] drivers/net/ethernet/qualcomm/rmnet/rmnet_config.c:386 suspicious rcu_dereference_check() !
[ 146.634742][ T1174]
[ 146.634742][ T1174] other info that might help us debug this:
[ 146.634742][ T1174]
[ 146.645992][ T1174]
[ 146.645992][ T1174] rcu_scheduler_active = 2, debug_locks = 1
[ 146.646937][ T1174] 5 locks held by ping/1174:
[ 146.647609][ T1174] #0: ffff8880c31dea70 (sk_lock-AF_INET){+.+.}, at: raw_sendmsg+0xab8/0x2980
[ 146.662463][ T1174] #1: ffffffff93925660 (rcu_read_lock_bh){....}, at: ip_finish_output2+0x243/0x2150
[ 146.671696][ T1174] #2: ffffffff93925660 (rcu_read_lock_bh){....}, at: __dev_queue_xmit+0x213/0x2940
[ 146.673064][ T1174] #3: ffff8880c19ecd58 (&dev->qdisc_running_key#7){+...}, at: ip_finish_output2+0x714/0x2150
[ 146.690358][ T1174] #4: ffff8880c5796898 (&dev->qdisc_xmit_lock_key#3){+.-.}, at: sch_direct_xmit+0x1e2/0x1020
[ 146.699875][ T1174]
[ 146.699875][ T1174] stack backtrace:
[ 146.701091][ T1174] CPU: 0 PID: 1174 Comm: ping Not tainted 5.6.0-rc1+ #447
[ 146.705215][ T1174] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
[ 146.706565][ T1174] Call Trace:
[ 146.707102][ T1174] dump_stack+0x96/0xdb
[ 146.708007][ T1174] rmnet_get_port.part.9+0x76/0x80 [rmnet]
[ 146.709233][ T1174] rmnet_egress_handler+0x107/0x420 [rmnet]
[ 146.710492][ T1174] ? sch_direct_xmit+0x1e2/0x1020
[ 146.716193][ T1174] rmnet_vnd_start_xmit+0x3d/0xa0 [rmnet]
[ 146.717012][ T1174] dev_hard_start_xmit+0x160/0x740
[ 146.717854][ T1174] sch_direct_xmit+0x265/0x1020
[ 146.718577][ T1174] ? register_lock_class+0x14d0/0x14d0
[ 146.719429][ T1174] ? dev_watchdog+0xac0/0xac0
[ 146.723738][ T1174] ? __dev_queue_xmit+0x15fd/0x2940
[ 146.724469][ T1174] ? lock_acquire+0x164/0x3b0
[ 146.725172][ T1174] __dev_queue_xmit+0x20c7/0x2940
[ ... ]
Fixes: ceed73a2cf4a ("drivers: net: ethernet: qualcomm: rmnet: Initial implementation")
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.