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, xmei5@asu.edu,
tgopinath@linux.microsoft.com, kys@microsoft.com,
blbllhy@gmail.com
Subject: [PATCH] gtp: add synchronize_net() in gtp_newlink() error path to prevent use-after-free
Date: Tue, 18 Aug 2026 21:48:58 -0400 [thread overview]
Message-ID: <20260819014858.76707-1-blbllhy@gmail.com> (raw)
gtp_newlink()'s error path frees tid_hash and addr_hash without
waiting for an RCU grace period after clearing sk_user_data. A
concurrent gtp_encap_recv() in softirq may still hold the gtp_dev
pointer obtained via rcu_dereference_sk_user_data() and access the
freed memory.
BUG: KASAN: slab-use-after-free in gtp0_pdp_find+0x1f6/0x200 (gtp.c:152)
Call Trace:
<IRQ>
gtp0_pdp_find+0x1f6/0x200
gtp_encap_recv+0x527/0x24b0
udp_queue_rcv_one_skb+0x75f/0xc10
Add synchronize_net() before the kfree calls in out_hashtable, which
covers all error paths from both gtp_encap_enable() and
gtp_create_sockets().
Fixes: 459aa660eb1d8ce6 ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)")
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, 2 insertions(+)
diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 9a12cc53da00..f11bcc0c0ac4 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -1543,6 +1543,8 @@ static int gtp_newlink(struct net_device *dev,
out_encap:
gtp_encap_disable(gtp);
out_hashtable:
+ /* Wait for RCU readers that may still reference this gtp_dev. */
+ synchronize_net();
kfree(gtp->addr_hash);
kfree(gtp->tid_hash);
return err;
--
2.52.0
reply other threads:[~2026-08-19 1:49 UTC|newest]
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