From: "Cen Zhang (Microsoft)" <blbllhy@gmail.com>
To: pablo@netfilter.org, laforge@gnumonks.org, andrew+netdev@lunn.ch,
davem@davemloft.net, edumazet@google.com, kuba@kernel.org,
pabeni@redhat.com
Cc: osmocom-net-gprs@lists.osmocom.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org,
AutonomousCodeSecurity@microsoft.com,
tgopinath@linux.microsoft.com, kys@microsoft.com,
blbllhy@gmail.com, "Xiang Mei (Microsoft)" <xmei5@asu.edu>
Subject: [PATCH net] gtp: fix NULL pointer dereference in gtp0_handle_echo_resp()
Date: Sat, 15 Aug 2026 23:52:05 -0400 [thread overview]
Message-ID: <20260816035205.57966-1-blbllhy@gmail.com> (raw)
In gtp_create_sockets(), gtp->sk_created is set to true before gtp->sk0
and gtp->sk1u are assigned. A concurrent GTP Echo Response packet on
another CPU observes sk_created == true and dereferences the still-NULL
gtp->sk0 in gtp0_handle_echo_resp(), causing a kernel panic.
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
RIP: 0010:gtp_encap_recv (drivers/net/gtp.c:542 gtp0_handle_echo_resp)
Call Trace:
<IRQ>
udp_queue_rcv_one_skb
ip_protocol_deliver_rcu
ip_local_deliver
Kernel panic - not syncing: Fatal exception in interrupt
Reorder the assignments so that gtp->sk0 and gtp->sk1u are fully visible
before gtp->sk_created is set to true. This ensures no concurrent packet
path can observe the flag without valid socket pointers.
Fixes: b20dc3c68458 ("gtp: Allow to create GTP device without FDs")
Reported-by: AutonomousCodeSecurity@microsoft.com
Reported-by: Xiang Mei (Microsoft) <xmei5@asu.edu>
Reported-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
Signed-off-by: Cen Zhang (Microsoft) <blbllhy@gmail.com>
---
drivers/net/gtp.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 9a12cc53da00..2b5a8f6d24d0 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -1456,9 +1456,9 @@ static int gtp_create_sockets(struct gtp_dev *gtp, const struct nlattr *nla,
return PTR_ERR(sk1u);
}
- gtp->sk_created = true;
gtp->sk0 = sk0;
gtp->sk1u = sk1u;
+ gtp->sk_created = true;
return 0;
}
--
2.52.0
reply other threads:[~2026-08-16 3:52 UTC|newest]
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