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gtp: hold RCU for the device lookup when adding a PDP context

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gtp_genl_new_pdp() calls gtp_find_dev(), which looks the device up with
dev_get_by_index_rcu(). Since commit e2d1baca2b ("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: e2d1baca2b ("gtp: remove useless rcu_read_lock()")
Signed-off-by: Anil Kaushik <anilkaushikwireless@gmail.com>
Link: https://patch.msgid.link/20261016093225.1036375-3-anilkaushikwireless@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Anil Kaushik 2026-10-16 09:32:23 +00:00 committed by Paolo Abeni
parent 758d8928d2
commit fe3e1a42fb
1 changed files with 3 additions and 0 deletions
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3
drivers/net/gtp.c
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@ -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;