gtp_genl_new_pdp() calls gtp_find_dev(), which looks the device up with dev_get_by_index_rcu(). Since commit e2d1baca2b33 ("gtp: remove useless rcu_read_lock()"), this only runs under the rtnl lock, and kernels with CONFIG_PROVE_RCU_LIST warn: WARNING: suspicious RCU usage net/core/dev.c:1047 RCU-list traversed in non-reader section!! ... dev_get_by_index_rcu gtp_find_dev gtp_genl_new_pdp Hold the RCU read lock around the lookup only: gtp_pdp_add() allocates with GFP_KERNEL, and the rtnl lock keeps the device alive afterwards. Found with the gtp selftest on a debug kernel. Fixes: e2d1baca2b33 ("gtp: remove useless rcu_read_lock()") Signed-off-by: Anil Kaushik --- drivers/net/gtp.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index 99836b773e5c..15b5d845fc3b 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c @@ -2050,7 +2050,10 @@ static int gtp_genl_new_pdp(struct sk_buff *skb, struct genl_info *info) rtnl_lock(); + /* the rtnl lock keeps the device alive once found */ + rcu_read_lock(); gtp = gtp_find_dev(sock_net(skb->sk), info->attrs); + rcu_read_unlock(); if (!gtp) { err = -ENODEV; goto out_unlock; -- 2.25.1