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FAILED: patch "[PATCH] gtp: serialize PDP context updates" failed to apply to 5.15-stable tree

PATCH New [email protected] 2 participants 2 messages Aug 31 – Sep 1

Subsystems (3)
Network drivers Stable branch GTP (GPRS Tunneling Protocol)
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[email protected]

author maintainer
#0 lore raw

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 498386b6d402737db1e2eeed4c385acbf0ef9e34
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026083100-implosive-divinity-5dca@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 498386b6d402737db1e2eeed4c385acbf0ef9e34 Mon Sep 17 00:00:00 2001
From: Qing Ming <[email protected]>
Date: Tue, 18 Aug 2026 23:00:00 +0800
Subject: [PATCH] gtp: serialize PDP context updates

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 simple 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 gtp_pdp_add(), gtp_genl_del_pdp(), and gtp_dellink() with a shared mutex. Keep the mutex held until the final use of a PDP context in the NEWPDP path, and keep the RCU read-side section around the complete PDP context use in the DELPDP path.

Fixes 459aa660eb1d ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)")
Cc [email protected]
Signed-off-by Qing Ming <[email protected]>
Link https://patch.msgid.link/[email protected] open here
Signed-off-by Jakub Kicinski <[email protected]>
drivers/net/gtp.c +17 -4
index 9a12cc53da00..2f6e77cce385 100644
@@ -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>

@@ -108,6 +109,7 @@ struct gtp_net {
 };
 
 static u32 gtp_h_initval;
+static DEFINE_MUTEX(gtp_pdp_lock);
 
 static struct genl_family gtp_genl_family;
 

@@ -151,7 +153,8 @@ static struct pdp_ctx *gtp0_pdp_find(struct gtp_dev *gtp, u64 tid, u16 family)
 
 	head = &gtp->tid_hash[gtp0_hashfn(tid) % gtp->hash_size];
 
-	hlist_for_each_entry_rcu(pdp, head, hlist_tid) {
+	hlist_for_each_entry_rcu(pdp, head, hlist_tid,
+				 lockdep_is_held(&gtp_pdp_lock)) {
 		if (pdp->af == family &&
 		    pdp->gtp_version == GTP_V0 &&
 		    pdp->u.v0.tid == tid)

@@ -168,7 +171,8 @@ static struct pdp_ctx *gtp1_pdp_find(struct gtp_dev *gtp, u32 tid, u16 family)
 
 	head = &gtp->tid_hash[gtp1u_hashfn(tid) % gtp->hash_size];
 
-	hlist_for_each_entry_rcu(pdp, head, hlist_tid) {
+	hlist_for_each_entry_rcu(pdp, head, hlist_tid,
+				 lockdep_is_held(&gtp_pdp_lock)) {
 		if (pdp->af == family &&
 		    pdp->gtp_version == GTP_V1 &&
 		    pdp->u.v1.i_tei == tid)

@@ -185,7 +189,8 @@ static struct pdp_ctx *ipv4_pdp_find(struct gtp_dev *gtp, __be32 ms_addr)
 
 	head = &gtp->addr_hash[ipv4_hashfn(ms_addr) % gtp->hash_size];
 
-	hlist_for_each_entry_rcu(pdp, head, hlist_addr) {
+	hlist_for_each_entry_rcu(pdp, head, hlist_addr,
+				 lockdep_is_held(&gtp_pdp_lock)) {
 		if (pdp->af == AF_INET &&
 		    pdp->ms.addr.s_addr == ms_addr)
 			return pdp;

@@ -220,7 +225,8 @@ static struct pdp_ctx *ipv6_pdp_find(struct gtp_dev *gtp,
 
 	head = &gtp->addr_hash[ipv6_hashfn(ms_addr) % gtp->hash_size];
 
-	hlist_for_each_entry_rcu(pdp, head, hlist_addr) {
+	hlist_for_each_entry_rcu(pdp, head, hlist_addr,
+				 lockdep_is_held(&gtp_pdp_lock)) {
 		if (pdp->af == AF_INET6 &&
 		    ipv6_pdp_addr_equal(&pdp->ms.addr6, ms_addr))
 			return pdp;

@@ -1555,9 +1561,11 @@ static void gtp_dellink(struct net_device *dev, struct list_head *head)
 	struct pdp_ctx *pctx;
 	int i;
 
+	mutex_lock(&gtp_pdp_lock);
 	for (i = 0; i < gtp->hash_size; i++)
 		hlist_for_each_entry_safe(pctx, next, &gtp->tid_hash[i], hlist_tid)
 			pdp_context_delete(pctx);
+	mutex_unlock(&gtp_pdp_lock);
 
 	list_del(&gtp->list);
 	unregister_netdevice_queue(dev, head);

@@ -2053,6 +2061,7 @@ static int gtp_genl_new_pdp(struct sk_buff *skb, struct genl_info *info)
 		goto out_unlock;
 	}
 
+	mutex_lock(&gtp_pdp_lock);
 	pctx = gtp_pdp_add(gtp, sk, info);
 	if (IS_ERR(pctx)) {
 		err = PTR_ERR(pctx);

@@ -2060,6 +2069,7 @@ static int gtp_genl_new_pdp(struct sk_buff *skb, struct genl_info *info)
 		gtp_tunnel_notify(pctx, GTP_CMD_NEWPDP, GFP_KERNEL);
 		err = 0;
 	}
+	mutex_unlock(&gtp_pdp_lock);
 
 out_unlock:
 	rtnl_unlock();

@@ -2134,6 +2144,8 @@ 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();
 
 	pctx = gtp_find_pdp(sock_net(skb->sk), info->attrs);

@@ -2154,6 +2166,7 @@ static int gtp_genl_del_pdp(struct sk_buff *skb, struct genl_info *info)
 
 out_unlock:
 	rcu_read_unlock();
+	mutex_unlock(&gtp_pdp_lock);
 	return err;
 }
maintainer
#1 lore raw

PATCH 1/1 gtp: serialize PDP context updates

From: Qing Ming <[email protected]>

[ Upstream commit 498386b6d402737db1e2eeed4c385acbf0ef9e34 ]

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 simple 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 gtp_pdp_add(), gtp_genl_del_pdp(), and gtp_dellink() with a shared mutex. Keep the mutex held until the final use of a PDP context in the NEWPDP path, and keep the RCU read-side section around the complete PDP context use in the DELPDP path.

Fixes 459aa660eb1d ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)")
Cc [email protected]
Signed-off-by Qing Ming <[email protected]>
Link https://patch.msgid.link/[email protected] open here
Signed-off-by Jakub Kicinski <[email protected]>
[ adapted the locking changes to the older IPv4-only PDP context API and omitted the absent IPv6 lookup hunk. ]
Signed-off-by Sasha Levin <[email protected]>
---
 drivers/net/gtp.c | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)
drivers/net/gtp.c +15 -3
index 8f76fd927ff4a..57698316a2bf0 100644
@@ -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>

@@ -82,6 +83,7 @@ struct gtp_net {
 };
 
 static u32 gtp_h_initval;
+static DEFINE_MUTEX(gtp_pdp_lock);
 
 static void pdp_context_delete(struct pdp_ctx *pctx);
 

@@ -109,7 +111,8 @@ static struct pdp_ctx *gtp0_pdp_find(struct gtp_dev *gtp, u64 tid)
 
 	head = &gtp->tid_hash[gtp0_hashfn(tid) % gtp->hash_size];
 
-	hlist_for_each_entry_rcu(pdp, head, hlist_tid) {
+	hlist_for_each_entry_rcu(pdp, head, hlist_tid,
+				 lockdep_is_held(&gtp_pdp_lock)) {
 		if (pdp->gtp_version == GTP_V0 &&
 		    pdp->u.v0.tid == tid)
 			return pdp;

@@ -125,7 +128,8 @@ static struct pdp_ctx *gtp1_pdp_find(struct gtp_dev *gtp, u32 tid)
 
 	head = &gtp->tid_hash[gtp1u_hashfn(tid) % gtp->hash_size];
 
-	hlist_for_each_entry_rcu(pdp, head, hlist_tid) {
+	hlist_for_each_entry_rcu(pdp, head, hlist_tid,
+				 lockdep_is_held(&gtp_pdp_lock)) {
 		if (pdp->gtp_version == GTP_V1 &&
 		    pdp->u.v1.i_tei == tid)
 			return pdp;

@@ -141,7 +145,8 @@ static struct pdp_ctx *ipv4_pdp_find(struct gtp_dev *gtp, __be32 ms_addr)
 
 	head = &gtp->addr_hash[ipv4_hashfn(ms_addr) % gtp->hash_size];
 
-	hlist_for_each_entry_rcu(pdp, head, hlist_addr) {
+	hlist_for_each_entry_rcu(pdp, head, hlist_addr,
+				 lockdep_is_held(&gtp_pdp_lock)) {
 		if (pdp->af == AF_INET &&
 		    pdp->ms_addr_ip4.s_addr == ms_addr)
 			return pdp;

@@ -720,9 +725,11 @@ static void gtp_dellink(struct net_device *dev, struct list_head *head)
 	struct pdp_ctx *pctx;
 	int i;
 
+	mutex_lock(&gtp_pdp_lock);
 	for (i = 0; i < gtp->hash_size; i++)
 		hlist_for_each_entry_safe(pctx, next, &gtp->tid_hash[i], hlist_tid)
 			pdp_context_delete(pctx);
+	mutex_unlock(&gtp_pdp_lock);
 
 	list_del(&gtp->list);
 	unregister_netdevice_queue(dev, head);

@@ -1110,6 +1117,7 @@ static int gtp_genl_new_pdp(struct sk_buff *skb, struct genl_info *info)
 		goto out_unlock;
 	}
 
+	mutex_lock(&gtp_pdp_lock);
 	pctx = gtp_pdp_add(gtp, sk, info);
 	if (IS_ERR(pctx)) {
 		err = PTR_ERR(pctx);

@@ -1117,6 +1125,7 @@ static int gtp_genl_new_pdp(struct sk_buff *skb, struct genl_info *info)
 		gtp_tunnel_notify(pctx, GTP_CMD_NEWPDP, GFP_KERNEL);
 		err = 0;
 	}
+	mutex_unlock(&gtp_pdp_lock);
 
 out_unlock:
 	rtnl_unlock();

@@ -1171,6 +1180,8 @@ 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();
 
 	pctx = gtp_find_pdp(sock_net(skb->sk), info->attrs);

@@ -1191,6 +1202,7 @@ static int gtp_genl_del_pdp(struct sk_buff *skb, struct genl_info *info)
 
 out_unlock:
 	rcu_read_unlock();
+	mutex_unlock(&gtp_pdp_lock);
 	return err;
 }
Signature · 1 line
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