FAILED: patch "[PATCH] net: phonet: free phonet_device after RCU grace period" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] net: phonet: free phonet_device after RCU grace period" failed to apply to 5.15-stable tree

[gregkh]

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 <stable@vger.kernel.org>.

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 71de0177b28da751f407581a4515cf4d762f6296
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026061547-discourse-faceless-4af5@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 71de0177b28da751f407581a4515cf4d762f6296 Mon Sep 17 00:00:00 2001
From: Santosh Kalluri <santosh.kalluri129@gmail.com>
Date: Wed, 3 Jun 2026 17:08:43 -0700
Subject: [PATCH] net: phonet: free phonet_device after RCU grace period
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

phonet_device_destroy() removes a phonet_device from the per-net device
list with list_del_rcu(), but frees it immediately. RCU readers walking
the same list can still hold a pointer to the object after it has been
removed, leading to a slab-use-after-free.

Use kfree_rcu(), matching the lifetime rule already used by
phonet_address_del() for the same object type.

Fixes: eeb74a9d45f7 ("Phonet: convert devices list to RCU")
Cc: stable@vger.kernel.org
Signed-off-by: Santosh Kalluri <santosh.kalluri129@gmail.com>
Acked-by: Rémi Denis-Courmont <remi@remlab.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/phonet/pn_dev.c b/net/phonet/pn_dev.c
index 86325b7fc1b6..ad44831d6745 100644
--- a/net/phonet/pn_dev.c
+++ b/net/phonet/pn_dev.c
@@ -108,7 +108,7 @@ static void phonet_device_destroy(struct net_device *dev)
 		for_each_set_bit(addr, pnd->addrs, 64)
 			phonet_address_notify(net, RTM_DELADDR, ifindex, addr);
 
-		kfree(pnd);
+		kfree_rcu(pnd, rcu);
 	}
 }
 

[PATCH 5.15.y 1/3] phonet: Pass ifindex to fill_addr().

[Sasha Levin]

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 08a9572be36819b5d9011604edfa5db6c5062a7a ]

We will convert addr_doit() and getaddr_dumpit() to RCU, both
of which call fill_addr().

The former will call phonet_address_notify() outside of RCU
due to GFP_KERNEL, so dev will not be available in fill_addr().

Let's pass ifindex directly to fill_addr().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Stable-dep-of: 71de0177b28d ("net: phonet: free phonet_device after RCU grace period")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/phonet/pn_netlink.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/net/phonet/pn_netlink.c b/net/phonet/pn_netlink.c
index dd4c7e9a634fbe..6b50e4d526682f 100644
--- a/net/phonet/pn_netlink.c
+++ b/net/phonet/pn_netlink.c
@@ -19,7 +19,7 @@
 
 /* Device address handling */
 
-static int fill_addr(struct sk_buff *skb, struct net_device *dev, u8 addr,
+static int fill_addr(struct sk_buff *skb, u32 ifindex, u8 addr,
 		     u32 portid, u32 seq, int event);
 
 void phonet_address_notify(int event, struct net_device *dev, u8 addr)
@@ -31,7 +31,8 @@ void phonet_address_notify(int event, struct net_device *dev, u8 addr)
 			nla_total_size(1), GFP_KERNEL);
 	if (skb == NULL)
 		goto errout;
-	err = fill_addr(skb, dev, addr, 0, 0, event);
+
+	err = fill_addr(skb, dev->ifindex, addr, 0, 0, event);
 	if (err < 0) {
 		WARN_ON(err == -EMSGSIZE);
 		kfree_skb(skb);
@@ -92,8 +93,8 @@ static int addr_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
 	return err;
 }
 
-static int fill_addr(struct sk_buff *skb, struct net_device *dev, u8 addr,
-			u32 portid, u32 seq, int event)
+static int fill_addr(struct sk_buff *skb, u32 ifindex, u8 addr,
+		     u32 portid, u32 seq, int event)
 {
 	struct ifaddrmsg *ifm;
 	struct nlmsghdr *nlh;
@@ -107,7 +108,7 @@ static int fill_addr(struct sk_buff *skb, struct net_device *dev, u8 addr,
 	ifm->ifa_prefixlen = 0;
 	ifm->ifa_flags = IFA_F_PERMANENT;
 	ifm->ifa_scope = RT_SCOPE_LINK;
-	ifm->ifa_index = dev->ifindex;
+	ifm->ifa_index = ifindex;
 	if (nla_put_u8(skb, IFA_LOCAL, addr))
 		goto nla_put_failure;
 	nlmsg_end(skb, nlh);
@@ -140,7 +141,7 @@ static int getaddr_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
 			if (addr_idx++ < addr_start_idx)
 				continue;
 
-			if (fill_addr(skb, pnd->netdev, addr << 2,
+			if (fill_addr(skb, pnd->netdev->ifindex, addr << 2,
 					 NETLINK_CB(cb->skb).portid,
 					cb->nlh->nlmsg_seq, RTM_NEWADDR) < 0)
 				goto out;
-- 
2.53.0

[PATCH 5.15.y 2/3] phonet: Pass net and ifindex to phonet_address_notify().

[Sasha Levin]

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 68ed5c38b512b734caf3da1f87db4a99fcfe3002 ]

Currently, phonet_address_notify() fetches netns and ifindex from dev.

Once addr_doit() is converted to RCU, phonet_address_notify() will be
called outside of RCU due to GFP_KERNEL, and dev will be unavailable
there.

Let's pass net and ifindex to phonet_address_notify().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Stable-dep-of: 71de0177b28d ("net: phonet: free phonet_device after RCU grace period")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/net/phonet/pn_dev.h |  2 +-
 net/phonet/pn_dev.c         | 10 +++++++---
 net/phonet/pn_netlink.c     | 12 ++++++------
 3 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/include/net/phonet/pn_dev.h b/include/net/phonet/pn_dev.h
index 05b49d4d2b1116..216677e56b41ee 100644
--- a/include/net/phonet/pn_dev.h
+++ b/include/net/phonet/pn_dev.h
@@ -33,7 +33,7 @@ int phonet_address_add(struct net_device *dev, u8 addr);
 int phonet_address_del(struct net_device *dev, u8 addr);
 u8 phonet_address_get(struct net_device *dev, u8 addr);
 int phonet_address_lookup(struct net *net, u8 addr);
-void phonet_address_notify(int event, struct net_device *dev, u8 addr);
+void phonet_address_notify(struct net *net, int event, u32 ifindex, u8 addr);
 
 int phonet_route_add(struct net_device *dev, u8 daddr);
 int phonet_route_del(struct net_device *dev, u8 daddr);
diff --git a/net/phonet/pn_dev.c b/net/phonet/pn_dev.c
index cde671d29d5dd3..2e7d850dc72668 100644
--- a/net/phonet/pn_dev.c
+++ b/net/phonet/pn_dev.c
@@ -98,10 +98,13 @@ static void phonet_device_destroy(struct net_device *dev)
 	mutex_unlock(&pndevs->lock);
 
 	if (pnd) {
+		struct net *net = dev_net(dev);
+		u32 ifindex = dev->ifindex;
 		u8 addr;
 
 		for_each_set_bit(addr, pnd->addrs, 64)
-			phonet_address_notify(RTM_DELADDR, dev, addr);
+			phonet_address_notify(net, RTM_DELADDR, ifindex, addr);
+
 		kfree(pnd);
 	}
 }
@@ -244,8 +247,9 @@ static int phonet_device_autoconf(struct net_device *dev)
 	ret = phonet_address_add(dev, req.ifr_phonet_autoconf.device);
 	if (ret)
 		return ret;
-	phonet_address_notify(RTM_NEWADDR, dev,
-				req.ifr_phonet_autoconf.device);
+
+	phonet_address_notify(dev_net(dev), RTM_NEWADDR, dev->ifindex,
+			      req.ifr_phonet_autoconf.device);
 	return 0;
 }
 
diff --git a/net/phonet/pn_netlink.c b/net/phonet/pn_netlink.c
index 6b50e4d526682f..c4c9fda4c3de14 100644
--- a/net/phonet/pn_netlink.c
+++ b/net/phonet/pn_netlink.c
@@ -22,7 +22,7 @@
 static int fill_addr(struct sk_buff *skb, u32 ifindex, u8 addr,
 		     u32 portid, u32 seq, int event);
 
-void phonet_address_notify(int event, struct net_device *dev, u8 addr)
+void phonet_address_notify(struct net *net, int event, u32 ifindex, u8 addr)
 {
 	struct sk_buff *skb;
 	int err = -ENOBUFS;
@@ -32,17 +32,17 @@ void phonet_address_notify(int event, struct net_device *dev, u8 addr)
 	if (skb == NULL)
 		goto errout;
 
-	err = fill_addr(skb, dev->ifindex, addr, 0, 0, event);
+	err = fill_addr(skb, ifindex, addr, 0, 0, event);
 	if (err < 0) {
 		WARN_ON(err == -EMSGSIZE);
 		kfree_skb(skb);
 		goto errout;
 	}
-	rtnl_notify(skb, dev_net(dev), 0,
-		    RTNLGRP_PHONET_IFADDR, NULL, GFP_KERNEL);
+
+	rtnl_notify(skb, net, 0, RTNLGRP_PHONET_IFADDR, NULL, GFP_KERNEL);
 	return;
 errout:
-	rtnl_set_sk_err(dev_net(dev), RTNLGRP_PHONET_IFADDR, err);
+	rtnl_set_sk_err(net, RTNLGRP_PHONET_IFADDR, err);
 }
 
 static const struct nla_policy ifa_phonet_policy[IFA_MAX+1] = {
@@ -89,7 +89,7 @@ static int addr_doit(struct sk_buff *skb, struct nlmsghdr *nlh,
 	else
 		err = phonet_address_del(dev, pnaddr);
 	if (!err)
-		phonet_address_notify(nlh->nlmsg_type, dev, pnaddr);
+		phonet_address_notify(net, nlh->nlmsg_type, ifm->ifa_index, pnaddr);
 	return err;
 }
 
-- 
2.53.0

[PATCH 5.15.y 3/3] net: phonet: free phonet_device after RCU grace period

[Sasha Levin]

From: Santosh Kalluri <santosh.kalluri129@gmail.com>

[ Upstream commit 71de0177b28da751f407581a4515cf4d762f6296 ]

phonet_device_destroy() removes a phonet_device from the per-net device
list with list_del_rcu(), but frees it immediately. RCU readers walking
the same list can still hold a pointer to the object after it has been
removed, leading to a slab-use-after-free.

Use kfree_rcu(), matching the lifetime rule already used by
phonet_address_del() for the same object type.

Fixes: eeb74a9d45f7 ("Phonet: convert devices list to RCU")
Cc: stable@vger.kernel.org
Signed-off-by: Santosh Kalluri <santosh.kalluri129@gmail.com>
Acked-by: Rémi Denis-Courmont <remi@remlab.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/phonet/pn_dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/phonet/pn_dev.c b/net/phonet/pn_dev.c
index 2e7d850dc72668..3f020c362d6cde 100644
--- a/net/phonet/pn_dev.c
+++ b/net/phonet/pn_dev.c
@@ -105,7 +105,7 @@ static void phonet_device_destroy(struct net_device *dev)
 		for_each_set_bit(addr, pnd->addrs, 64)
 			phonet_address_notify(net, RTM_DELADDR, ifindex, addr);
 
-		kfree(pnd);
+		kfree_rcu(pnd, rcu);
 	}
 }
 
-- 
2.53.0