6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Cen Zhang (Microsoft) <redacted>
[ Upstream commit d989e22ae9802c52c56ad4284d0caf26696cf6ae ]
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: <redacted>
Reported-by: Xiang Mei (Microsoft) <redacted>
Reported-by: Cen Zhang (Microsoft) <redacted>
Signed-off-by: Cen Zhang (Microsoft) <redacted>
Link: https://patch.msgid.link/20260820020735.59474-1-blbllhy@gmail.com (local)
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/gtp.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 59c9bd459b2fb..0817ff58b8dab 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -1106,6 +1106,8 @@ static int gtp_newlink(struct net *src_net, 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;
--
2.53.0