Re: [PATCH net v3] gtp: serialize PDP context updates

On Tue, Aug 11, 2026 at 10:20:12AM +0800, Qing Ming wrote:

PDP contexts can be deleted through GTP_CMD_DELPDP or while the GTP network device is being unregistered. The latter is serialized by RTNL, but the generic-netlink delete path only holds RCU.

Running both paths concurrently can therefore make both paths delete the same PDP context. The issue was found through static analysis and reproduced on a KASAN-enabled kernel by a two-thread program racing GTP_CMD_DELPDP against RTM_DELLINK:

Oops: general protection fault, probably for non-canonical address KASAN: maybe wild-memory-access in range [0xdead000000000120-0xdead000000000127] RIP: gtp_genl_del_pdp+0x1c1/0x420 [gtp] RBP: dead000000000122

The second deletion dereferenced the poisoned hlist pprev pointer.

Serialize PDP context updates with a mutex shared by gtp_pdp_add(), gtp_genl_del_pdp(), and gtp_dellink().

Fixes: 459aa660eb1d ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)") Assisted-by: Codex:gpt-5 Signed-off-by: Qing Ming a0yami@mailbox.org

---

v3:

• Rebase onto net/main.

v2: https://lore.kernel.org/netdev/20260808124322.5800-1-a0yami@mailbox.org/

• Use a dedicated mutex instead of RTNL.
• Protect PDP add, delete, and link teardown with the same mutex.

drivers/net/gtp.c | 9 +++++++++ 1 file changed, 9 insertions(+)

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index 9a12cc53da00..8ee516debeed 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c

[...]

@@ -2134,6 +2140,8 @@ static int gtp_genl_del_pdp(struct sk_buff *skb, struct genl_info *info) if (!info->attrs[GTPA_VERSION]) return -EINVAL;

• mutex_lock(&gtp_pdp_lock);
• rcu_read_lock();

This rcu_read_lock() can go away after adding this new mutex.

pctx = gtp_find_pdp(sock_net(skb->sk), info->attrs); @@ -2154,6 +2162,7 @@ static int gtp_genl_del_pdp(struct sk_buff *skb, struct genl_info *info)

out_unlock: rcu_read_unlock();

This can go away too, for gtp_genl_del_pdp(), the mutex replaces this incorrect rcu read size lock.

Thanks.

• mutex_unlock(&gtp_pdp_lock); return err;

}

-- 2.53.0