[PATCH net v2] gtp: serialize PDP context updates
From: Qing Ming <hidden>
Date: 2026-08-08 12:44:06
Also in:
lkml
Subsystem:
gtp (gprs tunneling protocol), networking drivers, the rest · Maintainers:
Pablo Neira Ayuso, Harald Welte, Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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 <redacted>
---
v2:
- 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 427b91aca50d..161d004e34b6 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c@@ -12,6 +12,7 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt #include <linux/module.h> +#include <linux/mutex.h> #include <linux/skbuff.h> #include <linux/udp.h> #include <linux/rculist.h>
@@ -105,6 +106,7 @@ struct gtp_net { }; static u32 gtp_h_initval; +static DEFINE_MUTEX(gtp_pdp_lock); static struct genl_family gtp_genl_family;
@@ -1546,9 +1548,11 @@ static void gtp_dellink(struct net_device *dev, struct list_head *head) struct pdp_ctx *pctx; int i; + mutex_lock(>p_pdp_lock); for (i = 0; i < gtp->hash_size; i++) hlist_for_each_entry_safe(pctx, next, >p->tid_hash[i], hlist_tid) pdp_context_delete(pctx); + mutex_unlock(>p_pdp_lock); list_del_rcu(>p->list); unregister_netdevice_queue(dev, head);
@@ -1820,6 +1824,8 @@ static struct pdp_ctx *gtp_pdp_add(struct gtp_dev *gtp, struct sock *sk, __be32 ms_addr; int family; + guard(mutex)(>p_pdp_lock); + version = nla_get_u32(info->attrs[GTPA_VERSION]); if (info->attrs[GTPA_FAMILY])
@@ -2127,6 +2133,8 @@ static int gtp_genl_del_pdp(struct sk_buff *skb, struct genl_info *info) if (!info->attrs[GTPA_VERSION]) return -EINVAL; + mutex_lock(>p_pdp_lock); + rcu_read_lock(); pctx = gtp_find_pdp(sock_net(skb->sk), info->attrs);
@@ -2147,6 +2155,7 @@ static int gtp_genl_del_pdp(struct sk_buff *skb, struct genl_info *info) out_unlock: rcu_read_unlock(); + mutex_unlock(>p_pdp_lock); return err; }
--
2.53.0