From: Taehee Yoo ap420073@gmail.com

[ Upstream commit e198987e7dd7d3645a53875151cd6f8fc425b706 ]

gtp_encap_enable_socket() and gtp_encap_destroy() are not protected by rcu_read_lock(). and it's not safe to write sk->sk_user_data. This patch make these functions to use lock_sock() instead of rcu_dereference_sk_user_data().

Test commands: gtp-link add gtp1

Splat looks like: [ 83.238315] ============================= [ 83.239127] WARNING: suspicious RCU usage [ 83.239702] 5.2.0-rc6+ #49 Not tainted [ 83.240268] ----------------------------- [ 83.241205] drivers/net/gtp.c:799 suspicious rcu_dereference_check() usage! [ 83.243828] [ 83.243828] other info that might help us debug this: [ 83.243828] [ 83.246325] [ 83.246325] rcu_scheduler_active = 2, debug_locks = 1 [ 83.247314] 1 lock held by gtp-link/1008: [ 83.248523] #0: 0000000017772c7f (rtnl_mutex){+.+.}, at: __rtnl_newlink+0x5f5/0x11b0 [ 83.251503] [ 83.251503] stack backtrace: [ 83.252173] CPU: 0 PID: 1008 Comm: gtp-link Not tainted 5.2.0-rc6+ #49 [ 83.253271] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 [ 83.254562] Call Trace: [ 83.254995] dump_stack+0x7c/0xbb [ 83.255567] gtp_encap_enable_socket+0x2df/0x360 [gtp] [ 83.256415] ? gtp_find_dev+0x1a0/0x1a0 [gtp] [ 83.257161] ? memset+0x1f/0x40 [ 83.257843] gtp_newlink+0x90/0xa21 [gtp] [ 83.258497] ? __netlink_ns_capable+0xc3/0xf0 [ 83.259260] __rtnl_newlink+0xb9f/0x11b0 [ 83.260022] ? rtnl_link_unregister+0x230/0x230 [ ... ]

Fixes: 1e3a3abd8b28 ("gtp: make GTP sockets in gtp_newlink optional") Signed-off-by: Taehee Yoo ap420073@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/gtp.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index dba3869b61be..2756edd84abc 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c @@ -293,12 +293,14 @@ static void gtp_encap_destroy(struct sock *sk) { struct gtp_dev *gtp;

- gtp = rcu_dereference_sk_user_data(sk); + lock_sock(sk); + gtp = sk->sk_user_data; if (gtp) { udp_sk(sk)->encap_type = 0; rcu_assign_sk_user_data(sk, NULL); sock_put(sk); } + release_sock(sk); }

static void gtp_encap_disable_sock(struct sock *sk) @@ -798,7 +800,8 @@ static struct sock *gtp_encap_enable_socket(int fd, int type, goto out_sock; }

- if (rcu_dereference_sk_user_data(sock->sk)) { + lock_sock(sock->sk); + if (sock->sk->sk_user_data) { sk = ERR_PTR(-EBUSY); goto out_sock; } @@ -814,6 +817,7 @@ static struct sock *gtp_encap_enable_socket(int fd, int type, setup_udp_tunnel_sock(sock_net(sock->sk), sock, &tuncfg);

out_sock: + release_sock(sock->sk); sockfd_put(sock); return sk; }