FAILED: patch "[PATCH] ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()" failed to apply to 5.10-stable tree

FAILED: patch "[PATCH] ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()" failed to apply to 5.10-stable tree

[gregkh]

The patch below does not apply to the 5.10-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-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x f826df95332c07380206dbd54178b6eefb311aba
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026090351-marbling-tiny-a334@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From f826df95332c07380206dbd54178b6eefb311aba Mon Sep 17 00:00:00 2001
From: Andrea Mayer <andrea.mayer@uniroma2.it>
Date: Mon, 17 Aug 2026 15:26:44 +0200
Subject: [PATCH] ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()

ipv6_rpl_srh_rcv() dereferences idev from __in6_dev_get() without a NULL
check when reading idev->cnf.rpl_seg_enabled.

When the device's MTU drops below IPV6_MIN_MTU, addrconf_ifdown() clears
dev->ip6_ptr through RCU_INIT_POINTER(). A packet that passed the idev
check in ip6_rcv_core() can then reach ipv6_rpl_srh_rcv() with
dev->ip6_ptr already NULL.

Reproduced by flooding the receiving interface with ping6 traffic while
flapping its MTU between 1500 and 1200:

 BUG: KASAN: null-ptr-deref in ipv6_rpl_srh_rcv+0xb3/0x1070
 Read of size 4 at addr 00000000000006b4 by task ping6/394

 CPU: 2 UID: 0 PID: 394 Comm: ping6 Not tainted 7.2.0-rc7-micro-vm-dev-00095-g24ef02f934ee #240 PREEMPT(full)
 Call Trace:
  <IRQ>
  kasan_report+0xc6/0x100
  ipv6_rpl_srh_rcv+0xb3/0x1070
  ip6_protocol_deliver_rcu+0x759/0x9a0
  ip6_input_finish+0xa8/0x1b0
  ip6_input+0xe1/0x490
  ipv6_rcv+0x33d/0x460
  __netif_receive_skb_one_core+0xd6/0x130
  process_backlog+0x2cc/0xa00
  __napi_poll.constprop.0+0x56/0x270
  net_rx_action+0x327/0x730
  handle_softirqs+0x11e/0x630
  do_softirq+0xb3/0xf0
  </IRQ>

Both ipv6_rpl_srh_rcv() and ipv6_srh_rcv() are called only from
ipv6_rthdr_rcv(), which already has an idev lookup.

Fix the NULL dereference on the RPL path by checking idev in
ipv6_rthdr_rcv(), before it calls either function. The callees take idev as
an argument and no longer call __in6_dev_get(), so the packet is now
dropped in one place, with SKB_DROP_REASON_IPV6DISABLED on both paths.

Fixes: 8610c7c6e3bd ("net: ipv6: add support for rpl sr exthdr")
Cc: stable@vger.kernel.org
Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Tested-by: Xiang Mei <xmei5@asu.edu>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260817132644.2223-1-andrea.mayer@uniroma2.it
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 9c677eb1d1a6..51941ad656a3 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -368,23 +368,16 @@ static void seg6_update_csum(struct sk_buff *skb)
 			   (__be32 *)addr);
 }
 
-static int ipv6_srh_rcv(struct sk_buff *skb)
+static int ipv6_srh_rcv(struct sk_buff *skb, struct inet6_dev *idev)
 {
 	struct inet6_skb_parm *opt = IP6CB(skb);
 	struct net *net = dev_net(skb->dev);
 	struct ipv6_sr_hdr *hdr;
-	struct inet6_dev *idev;
 	struct in6_addr *addr;
 	int accept_seg6;
 
 	hdr = (struct ipv6_sr_hdr *)skb_transport_header(skb);
 
-	idev = __in6_dev_get(skb->dev);
-	if (!idev) {
-		kfree_skb(skb);
-		return -1;
-	}
-
 	accept_seg6 = min(READ_ONCE(net->ipv6.devconf_all->seg6_enabled),
 			  READ_ONCE(idev->cnf.seg6_enabled));
 
@@ -485,12 +478,11 @@ static int ipv6_srh_rcv(struct sk_buff *skb)
 	return -1;
 }
 
-static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
+static int ipv6_rpl_srh_rcv(struct sk_buff *skb, struct inet6_dev *idev)
 {
 	struct ipv6_rpl_sr_hdr *hdr, *ohdr, *chdr;
 	struct inet6_skb_parm *opt = IP6CB(skb);
 	struct net *net = dev_net(skb->dev);
-	struct inet6_dev *idev;
 	struct ipv6hdr *oldhdr;
 	unsigned int chdr_len;
 	unsigned char *buf;
@@ -499,8 +491,6 @@ static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
 	u64 n = 0;
 	u32 r;
 
-	idev = __in6_dev_get(skb->dev);
-
 	accept_rpl_seg = min(READ_ONCE(net->ipv6.devconf_all->rpl_seg_enabled),
 			     READ_ONCE(idev->cnf.rpl_seg_enabled));
 	if (!accept_rpl_seg) {
@@ -689,10 +679,14 @@ static int ipv6_rthdr_rcv(struct sk_buff *skb)
 	switch (hdr->type) {
 	case IPV6_SRCRT_TYPE_4:
 		/* segment routing */
-		return ipv6_srh_rcv(skb);
+		if (!idev)
+			goto disabled;
+		return ipv6_srh_rcv(skb, idev);
 	case IPV6_SRCRT_TYPE_3:
 		/* rpl segment routing */
-		return ipv6_rpl_srh_rcv(skb);
+		if (!idev)
+			goto disabled;
+		return ipv6_rpl_srh_rcv(skb, idev);
 	default:
 		break;
 	}
@@ -837,6 +831,10 @@ static int ipv6_rthdr_rcv(struct sk_buff *skb)
 	icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
 			  (&hdr->type) - skb_network_header(skb));
 	return -1;
+
+disabled:
+	kfree_skb_reason(skb, SKB_DROP_REASON_IPV6DISABLED);
+	return -1;
 }
 
 static const struct inet6_protocol rthdr_protocol = {

[PATCH 5.10.y 1/2] ipv6/addrconf: annotate data-races around devconf fields (II)

[Sasha Levin]

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 2f0ff05a44302c91af54a5f9efe1b65b7681540e ]

Final (?) round of this series.

Annotate lockless reads on following devconf fields,
because they be changed concurrently from /proc/net/ipv6/conf.

- accept_dad
- optimistic_dad
- use_optimistic
- use_oif_addrs_only
- ra_honor_pio_life
- keep_addr_on_down
- ndisc_notify
- ndisc_evict_nocarrier
- suppress_frag_ndisc
- addr_gen_mode
- seg6_enabled
- ioam6_enabled
- ioam6_id
- ioam6_id_wide
- drop_unicast_in_l2_multicast
- mldv[12]_unsolicited_report_interval
- force_mld_version
- force_tllao
- accept_untracked_na
- drop_unsolicited_na
- accept_source_route

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

[ Backport to 5.10: omit ioam6.c and annotations for fields and control
  flow only present in newer kernels. Preserve the applicable data-race
  annotations, and annotate rpl_seg_enabled as well so the dependent IPv6
  RPL fix applies against its expected context. ]

[ sashal: Reduced backport -- upstream 2f0ff05a44302 touches 7 file(s), this
  backport carries 6. Not backported here:
  net/ipv6/ioam6.c
  This note is generated from the file lists only; see the resolution record
  for the reasoning. ]

Stable-dep-of: f826df95332c ("ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/ipv6/addrconf.c  | 47 +++++++++++++++++++++++---------------------
 net/ipv6/exthdrs.c   | 20 +++++++++----------
 net/ipv6/ip6_input.c |  2 +-
 net/ipv6/mcast.c     | 14 ++++++-------
 net/ipv6/ndisc.c     | 12 +++++------
 net/ipv6/seg6_hmac.c |  8 +++++---
 6 files changed, 54 insertions(+), 49 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 3bb1855cdcb87..6d5a4a7fb18fe 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1492,15 +1492,17 @@ static inline int ipv6_saddr_preferred(int type)
 	return 0;
 }
 
-static bool ipv6_use_optimistic_addr(struct net *net,
-				     struct inet6_dev *idev)
+static bool ipv6_use_optimistic_addr(const struct net *net,
+				     const struct inet6_dev *idev)
 {
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
 	if (!idev)
 		return false;
-	if (!net->ipv6.devconf_all->optimistic_dad && !idev->cnf.optimistic_dad)
+	if (!READ_ONCE(net->ipv6.devconf_all->optimistic_dad) &&
+	    !READ_ONCE(idev->cnf.optimistic_dad))
 		return false;
-	if (!net->ipv6.devconf_all->use_optimistic && !idev->cnf.use_optimistic)
+	if (!READ_ONCE(net->ipv6.devconf_all->use_optimistic) &&
+	    !READ_ONCE(idev->cnf.use_optimistic))
 		return false;
 
 	return true;
@@ -1509,13 +1511,14 @@ static bool ipv6_use_optimistic_addr(struct net *net,
 #endif
 }
 
-static bool ipv6_allow_optimistic_dad(struct net *net,
-				      struct inet6_dev *idev)
+static bool ipv6_allow_optimistic_dad(const struct net *net,
+				      const struct inet6_dev *idev)
 {
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
 	if (!idev)
 		return false;
-	if (!net->ipv6.devconf_all->optimistic_dad && !idev->cnf.optimistic_dad)
+	if (!READ_ONCE(net->ipv6.devconf_all->optimistic_dad) &&
+	    !READ_ONCE(idev->cnf.optimistic_dad))
 		return false;
 
 	return true;
@@ -1797,7 +1800,7 @@ int ipv6_dev_get_saddr(struct net *net, const struct net_device *dst_dev,
 		idev = __in6_dev_get(dst_dev);
 		if ((dst_type & IPV6_ADDR_MULTICAST) ||
 		    dst.scope <= IPV6_ADDR_SCOPE_LINKLOCAL ||
-		    (idev && idev->cnf.use_oif_addrs_only)) {
+		    (idev && READ_ONCE(idev->cnf.use_oif_addrs_only))) {
 			use_oif_addr = true;
 		}
 	}
@@ -2628,8 +2631,8 @@ int addrconf_prefix_rcv_add_addr(struct net *net, struct net_device *dev,
 		};
 
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
-		if ((net->ipv6.devconf_all->optimistic_dad ||
-		     in6_dev->cnf.optimistic_dad) &&
+		if ((READ_ONCE(net->ipv6.devconf_all->optimistic_dad) ||
+		     READ_ONCE(in6_dev->cnf.optimistic_dad)) &&
 		    !net->ipv6.devconf_all->forwarding && sllao)
 			cfg.ifa_flags |= IFA_F_OPTIMISTIC;
 #endif
@@ -3226,8 +3229,8 @@ void addrconf_add_linklocal(struct inet6_dev *idev,
 	struct inet6_ifaddr *ifp;
 
 #ifdef CONFIG_IPV6_OPTIMISTIC_DAD
-	if ((dev_net(idev->dev)->ipv6.devconf_all->optimistic_dad ||
-	     idev->cnf.optimistic_dad) &&
+	if ((READ_ONCE(dev_net(idev->dev)->ipv6.devconf_all->optimistic_dad) ||
+	     READ_ONCE(idev->cnf.optimistic_dad)) &&
 	    !dev_net(idev->dev)->ipv6.devconf_all->forwarding)
 		cfg.ifa_flags |= IFA_F_OPTIMISTIC;
 #endif
@@ -3784,10 +3787,10 @@ static int addrconf_ifdown(struct net_device *dev, bool unregister)
 	 */
 	if (!unregister && !idev->cnf.disable_ipv6) {
 		/* aggregate the system setting and interface setting */
-		int _keep_addr = net->ipv6.devconf_all->keep_addr_on_down;
+		int _keep_addr = READ_ONCE(net->ipv6.devconf_all->keep_addr_on_down);
 
 		if (!_keep_addr)
-			_keep_addr = idev->cnf.keep_addr_on_down;
+			_keep_addr = READ_ONCE(idev->cnf.keep_addr_on_down);
 
 		keep_addr = (_keep_addr > 0);
 	}
@@ -4009,8 +4012,8 @@ static void addrconf_dad_begin(struct inet6_ifaddr *ifp)
 
 	net = dev_net(dev);
 	if (dev->flags&(IFF_NOARP|IFF_LOOPBACK) ||
-	    (net->ipv6.devconf_all->accept_dad < 1 &&
-	     idev->cnf.accept_dad < 1) ||
+	    (READ_ONCE(net->ipv6.devconf_all->accept_dad) < 1 &&
+	     READ_ONCE(idev->cnf.accept_dad) < 1) ||
 	    !(ifp->flags&IFA_F_TENTATIVE) ||
 	    ifp->flags & IFA_F_NODAD) {
 		bool send_na = false;
@@ -4102,8 +4105,8 @@ static void addrconf_dad_work(struct work_struct *w)
 		action = DAD_ABORT;
 		ifp->state = INET6_IFADDR_STATE_POSTDAD;
 
-		if ((dev_net(idev->dev)->ipv6.devconf_all->accept_dad > 1 ||
-		     idev->cnf.accept_dad > 1) &&
+		if ((READ_ONCE(dev_net(idev->dev)->ipv6.devconf_all->accept_dad) > 1 ||
+		     READ_ONCE(idev->cnf.accept_dad) > 1) &&
 		    !idev->cnf.disable_ipv6 &&
 		    !(ifp->flags & IFA_F_STABLE_PRIVACY)) {
 			struct in6_addr addr;
@@ -4241,8 +4244,8 @@ static void addrconf_dad_completed(struct inet6_ifaddr *ifp, bool bump_id,
 
 	/* send unsolicited NA if enabled */
 	if (send_na &&
-	    (ifp->idev->cnf.ndisc_notify ||
-	     dev_net(dev)->ipv6.devconf_all->ndisc_notify)) {
+	    (READ_ONCE(ifp->idev->cnf.ndisc_notify) ||
+	     READ_ONCE(dev_net(dev)->ipv6.devconf_all->ndisc_notify))) {
 		ndisc_send_na(dev, &in6addr_linklocal_allnodes, &ifp->addr,
 			      /*router=*/ !!ifp->idev->cnf.forwarding,
 			      /*solicited=*/ false, /*override=*/ true,
@@ -6389,7 +6392,7 @@ static int addrconf_sysctl_addr_gen_mode(struct ctl_table *ctl, int write,
 		} else if (&net->ipv6.devconf_all->addr_gen_mode == ctl->data) {
 			struct net_device *dev;
 
-			net->ipv6.devconf_dflt->addr_gen_mode = new_val;
+			WRITE_ONCE(net->ipv6.devconf_dflt->addr_gen_mode, new_val);
 			for_each_netdev(net, dev) {
 				idev = __in6_dev_get(dev);
 				if (idev &&
@@ -6400,7 +6403,7 @@ static int addrconf_sysctl_addr_gen_mode(struct ctl_table *ctl, int write,
 			}
 		}
 
-		*((u32 *)ctl->data) = new_val;
+		WRITE_ONCE(*((u32 *)ctl->data), new_val);
 	}
 
 out:
diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 0230fa98a3482..bc01761844194 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -368,9 +368,8 @@ static int ipv6_srh_rcv(struct sk_buff *skb)
 		return -1;
 	}
 
-	accept_seg6 = net->ipv6.devconf_all->seg6_enabled;
-	if (accept_seg6 > idev->cnf.seg6_enabled)
-		accept_seg6 = idev->cnf.seg6_enabled;
+	accept_seg6 = min(READ_ONCE(net->ipv6.devconf_all->seg6_enabled),
+			  READ_ONCE(idev->cnf.seg6_enabled));
 
 	if (!accept_seg6) {
 		kfree_skb(skb);
@@ -491,9 +490,8 @@ static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
 
 	idev = __in6_dev_get(skb->dev);
 
-	accept_rpl_seg = net->ipv6.devconf_all->rpl_seg_enabled;
-	if (accept_rpl_seg > idev->cnf.rpl_seg_enabled)
-		accept_rpl_seg = idev->cnf.rpl_seg_enabled;
+	accept_rpl_seg = min(READ_ONCE(net->ipv6.devconf_all->rpl_seg_enabled),
+			     READ_ONCE(idev->cnf.rpl_seg_enabled));
 
 	if (!accept_rpl_seg) {
 		kfree_skb(skb);
@@ -674,11 +672,13 @@ static int ipv6_rthdr_rcv(struct sk_buff *skb)
 	struct ipv6_rt_hdr *hdr;
 	struct rt0_hdr *rthdr;
 	struct net *net = dev_net(skb->dev);
-	int accept_source_route = net->ipv6.devconf_all->accept_source_route;
+	int accept_source_route;
 
-	idev = __in6_dev_get(skb->dev);
-	if (idev && accept_source_route > idev->cnf.accept_source_route)
-		accept_source_route = idev->cnf.accept_source_route;
+	accept_source_route = READ_ONCE(net->ipv6.devconf_all->accept_source_route);
+
+	if (idev)
+		accept_source_route = min(accept_source_route,
+					  READ_ONCE(idev->cnf.accept_source_route));
 
 	if (!pskb_may_pull(skb, skb_transport_offset(skb) + 8) ||
 	    !pskb_may_pull(skb, (skb_transport_offset(skb) +
diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 8cf5b10eee695..85e14f9df3a63 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -229,7 +229,7 @@ static struct sk_buff *ip6_rcv_core(struct sk_buff *skb, struct net_device *dev,
 	if (!ipv6_addr_is_multicast(&hdr->daddr) &&
 	    (skb->pkt_type == PACKET_BROADCAST ||
 	     skb->pkt_type == PACKET_MULTICAST) &&
-	    idev->cnf.drop_unicast_in_l2_multicast)
+	    READ_ONCE(idev->cnf.drop_unicast_in_l2_multicast))
 		goto err;
 
 	/* RFC4291 2.7
diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c
index c4a9866ea45b6..cdbff3dc89ced 100644
--- a/net/ipv6/mcast.c
+++ b/net/ipv6/mcast.c
@@ -162,9 +162,9 @@ static int unsolicited_report_interval(struct inet6_dev *idev)
 	int iv;
 
 	if (mld_in_v1_mode(idev))
-		iv = idev->cnf.mldv1_unsolicited_report_interval;
+		iv = READ_ONCE(idev->cnf.mldv1_unsolicited_report_interval);
 	else
-		iv = idev->cnf.mldv2_unsolicited_report_interval;
+		iv = READ_ONCE(idev->cnf.mldv2_unsolicited_report_interval);
 
 	return iv > 0 ? iv : 1;
 }
@@ -1218,15 +1218,15 @@ static bool mld_marksources(struct ifmcaddr6 *pmc, int nsrcs,
 
 static int mld_force_mld_version(const struct inet6_dev *idev)
 {
+	const struct net *net = dev_net(idev->dev);
+	int all_force;
+
+	all_force = READ_ONCE(net->ipv6.devconf_all->force_mld_version);
 	/* Normally, both are 0 here. If enforcement to a particular is
 	 * being used, individual device enforcement will have a lower
 	 * precedence over 'all' device (.../conf/all/force_mld_version).
 	 */
-
-	if (dev_net(idev->dev)->ipv6.devconf_all->force_mld_version != 0)
-		return dev_net(idev->dev)->ipv6.devconf_all->force_mld_version;
-	else
-		return idev->cnf.force_mld_version;
+	return all_force ?: READ_ONCE(idev->cnf.force_mld_version);
 }
 
 static bool mld_in_v2_mode_only(const struct inet6_dev *idev)
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index de389b519700d..e8e3ea61e0623 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -450,7 +450,7 @@ static void ip6_nd_hdr(struct sk_buff *skb,
 
 	rcu_read_lock();
 	idev = __in6_dev_get(skb->dev);
-	tclass = idev ? idev->cnf.ndisc_tclass : 0;
+	tclass = idev ? READ_ONCE(idev->cnf.ndisc_tclass) : 0;
 	rcu_read_unlock();
 
 	skb_push(skb, sizeof(*hdr));
@@ -538,7 +538,7 @@ void ndisc_send_na(struct net_device *dev, const struct in6_addr *daddr,
 		src_addr = solicited_addr;
 		if (ifp->flags & IFA_F_OPTIMISTIC)
 			override = false;
-		inc_opt |= ifp->idev->cnf.force_tllao;
+		inc_opt |= READ_ONCE(ifp->idev->cnf.force_tllao);
 		in6_ifa_put(ifp);
 	} else {
 		if (ipv6_dev_get_saddr(dev_net(dev), dev, daddr,
@@ -991,7 +991,7 @@ static void ndisc_recv_na(struct sk_buff *skb)
 	 * and thus should not be accepted.
 	 */
 	if (!msg->icmph.icmp6_solicited && idev &&
-	    idev->cnf.drop_unsolicited_na)
+	    READ_ONCE(idev->cnf.drop_unsolicited_na))
 		return;
 
 	if (!ndisc_parse_options(dev, msg->opt, ndoptlen, &ndopts)) {
@@ -1737,7 +1737,7 @@ static bool ndisc_suppress_frag_ndisc(struct sk_buff *skb)
 	if (!idev)
 		return true;
 	if (IP6CB(skb)->flags & IP6SKB_FRAGMENTED &&
-	    idev->cnf.suppress_frag_ndisc) {
+	    READ_ONCE(idev->cnf.suppress_frag_ndisc)) {
 		net_warn_ratelimited("Received fragmented ndisc packet. Carefully consider disabling suppress_frag_ndisc.\n");
 		return true;
 	}
@@ -1812,8 +1812,8 @@ static int ndisc_netdev_event(struct notifier_block *this, unsigned long event,
 		idev = in6_dev_get(dev);
 		if (!idev)
 			break;
-		if (idev->cnf.ndisc_notify ||
-		    net->ipv6.devconf_all->ndisc_notify)
+		if (READ_ONCE(idev->cnf.ndisc_notify) ||
+		    READ_ONCE(net->ipv6.devconf_all->ndisc_notify))
 			ndisc_send_unsol_na(dev);
 		in6_dev_put(idev);
 		break;
diff --git a/net/ipv6/seg6_hmac.c b/net/ipv6/seg6_hmac.c
index b52985c867c29..abccc86990c1a 100644
--- a/net/ipv6/seg6_hmac.c
+++ b/net/ipv6/seg6_hmac.c
@@ -243,6 +243,7 @@ bool seg6_hmac_validate_skb(struct sk_buff *skb)
 	struct sr6_tlv_hmac *tlv;
 	struct ipv6_sr_hdr *srh;
 	struct inet6_dev *idev;
+	int require_hmac;
 
 	idev = __in6_dev_get(skb->dev);
 	if (!idev)
@@ -252,16 +253,17 @@ bool seg6_hmac_validate_skb(struct sk_buff *skb)
 
 	tlv = seg6_get_tlv_hmac(srh);
 
+	require_hmac = READ_ONCE(idev->cnf.seg6_require_hmac);
 	/* mandatory check but no tlv */
-	if (idev->cnf.seg6_require_hmac > 0 && !tlv)
+	if (require_hmac > 0 && !tlv)
 		return false;
 
 	/* no check */
-	if (idev->cnf.seg6_require_hmac < 0)
+	if (require_hmac < 0)
 		return true;
 
 	/* check only if present */
-	if (idev->cnf.seg6_require_hmac == 0 && !tlv)
+	if (require_hmac == 0 && !tlv)
 		return true;
 
 	/* now, seg6_require_hmac >= 0 && tlv */
-- 
2.53.0

[PATCH 5.10.y 2/2] ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()

[Sasha Levin]

From: Andrea Mayer <andrea.mayer@uniroma2.it>

[ Upstream commit f826df95332c07380206dbd54178b6eefb311aba ]

ipv6_rpl_srh_rcv() dereferences idev from __in6_dev_get() without a NULL
check when reading idev->cnf.rpl_seg_enabled.

When the device's MTU drops below IPV6_MIN_MTU, addrconf_ifdown() clears
dev->ip6_ptr through RCU_INIT_POINTER(). A packet that passed the idev
check in ip6_rcv_core() can then reach ipv6_rpl_srh_rcv() with
dev->ip6_ptr already NULL.

Reproduced by flooding the receiving interface with ping6 traffic while
flapping its MTU between 1500 and 1200:

 BUG: KASAN: null-ptr-deref in ipv6_rpl_srh_rcv+0xb3/0x1070
 Read of size 4 at addr 00000000000006b4 by task ping6/394

 CPU: 2 UID: 0 PID: 394 Comm: ping6 Not tainted 7.2.0-rc7-micro-vm-dev-00095-g24ef02f934ee #240 PREEMPT(full)
 Call Trace:
  <IRQ>
  kasan_report+0xc6/0x100
  ipv6_rpl_srh_rcv+0xb3/0x1070
  ip6_protocol_deliver_rcu+0x759/0x9a0
  ip6_input_finish+0xa8/0x1b0
  ip6_input+0xe1/0x490
  ipv6_rcv+0x33d/0x460
  __netif_receive_skb_one_core+0xd6/0x130
  process_backlog+0x2cc/0xa00
  __napi_poll.constprop.0+0x56/0x270
  net_rx_action+0x327/0x730
  handle_softirqs+0x11e/0x630
  do_softirq+0xb3/0xf0
  </IRQ>

Both ipv6_rpl_srh_rcv() and ipv6_srh_rcv() are called only from
ipv6_rthdr_rcv(), which already has an idev lookup.

Fix the NULL dereference on the RPL path by checking idev in
ipv6_rthdr_rcv(), before it calls either function. The callees take idev as
an argument and no longer call __in6_dev_get(), so the packet is now
dropped in one place, with SKB_DROP_REASON_IPV6DISABLED on both paths.

Fixes: 8610c7c6e3bd ("net: ipv6: add support for rpl sr exthdr")
Cc: stable@vger.kernel.org
Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Tested-by: Xiang Mei <xmei5@asu.edu>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260817132644.2223-1-andrea.mayer@uniroma2.it
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Replaced kfree_skb_reason(skb, SKB_DROP_REASON_IPV6DISABLED) with kfree_skb(skb) for 5.10 compatibility. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/ipv6/exthdrs.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index bc01761844194..5584d3cf43742 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -351,23 +351,16 @@ static void seg6_update_csum(struct sk_buff *skb)
 			   (__be32 *)addr);
 }
 
-static int ipv6_srh_rcv(struct sk_buff *skb)
+static int ipv6_srh_rcv(struct sk_buff *skb, struct inet6_dev *idev)
 {
 	struct inet6_skb_parm *opt = IP6CB(skb);
 	struct net *net = dev_net(skb->dev);
 	struct ipv6_sr_hdr *hdr;
-	struct inet6_dev *idev;
 	struct in6_addr *addr;
 	int accept_seg6;
 
 	hdr = (struct ipv6_sr_hdr *)skb_transport_header(skb);
 
-	idev = __in6_dev_get(skb->dev);
-	if (!idev) {
-		kfree_skb(skb);
-		return -1;
-	}
-
 	accept_seg6 = min(READ_ONCE(net->ipv6.devconf_all->seg6_enabled),
 			  READ_ONCE(idev->cnf.seg6_enabled));
 
@@ -473,12 +466,11 @@ static int ipv6_srh_rcv(struct sk_buff *skb)
 	return -1;
 }
 
-static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
+static int ipv6_rpl_srh_rcv(struct sk_buff *skb, struct inet6_dev *idev)
 {
 	struct ipv6_rpl_sr_hdr *hdr, *ohdr, *chdr;
 	struct inet6_skb_parm *opt = IP6CB(skb);
 	struct net *net = dev_net(skb->dev);
-	struct inet6_dev *idev;
 	struct ipv6hdr *oldhdr;
 	struct in6_addr addr;
 	unsigned int chdr_len;
@@ -488,8 +480,6 @@ static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
 	u64 n = 0;
 	u32 r;
 
-	idev = __in6_dev_get(skb->dev);
-
 	accept_rpl_seg = min(READ_ONCE(net->ipv6.devconf_all->rpl_seg_enabled),
 			     READ_ONCE(idev->cnf.rpl_seg_enabled));
 
@@ -700,10 +690,14 @@ static int ipv6_rthdr_rcv(struct sk_buff *skb)
 	switch (hdr->type) {
 	case IPV6_SRCRT_TYPE_4:
 		/* segment routing */
-		return ipv6_srh_rcv(skb);
+		if (!idev)
+			goto disabled;
+		return ipv6_srh_rcv(skb, idev);
 	case IPV6_SRCRT_TYPE_3:
 		/* rpl segment routing */
-		return ipv6_rpl_srh_rcv(skb);
+		if (!idev)
+			goto disabled;
+		return ipv6_rpl_srh_rcv(skb, idev);
 	default:
 		break;
 	}
@@ -851,6 +845,10 @@ static int ipv6_rthdr_rcv(struct sk_buff *skb)
 	icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
 			  (&hdr->type) - skb_network_header(skb));
 	return -1;
+
+disabled:
+	kfree_skb(skb);
+	return -1;
 }
 
 static const struct inet6_protocol rthdr_protocol = {
-- 
2.53.0

[PATCH 5.10.y 1/2] ipv6/addrconf: annotate data-races around devconf fields (II)

[Sasha Levin]

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 2f0ff05a44302c91af54a5f9efe1b65b7681540e ]

Final (?) round of this series.

Annotate lockless reads on following devconf fields,
because they be changed concurrently from /proc/net/ipv6/conf.

- accept_dad
- optimistic_dad
- use_optimistic
- use_oif_addrs_only
- ra_honor_pio_life
- keep_addr_on_down
- ndisc_notify
- ndisc_evict_nocarrier
- suppress_frag_ndisc
- addr_gen_mode
- seg6_enabled
- ioam6_enabled
- ioam6_id
- ioam6_id_wide
- drop_unicast_in_l2_multicast
- mldv[12]_unsolicited_report_interval
- force_mld_version
- force_tllao
- accept_untracked_na
- drop_unsolicited_na
- accept_source_route

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Backport notes for Linux 5.10:

Keep only the routing-header annotations in net/ipv6/exthdrs.c. The
addrconf, input, multicast, neighbour-discovery, HMAC and IOAM hunks are
not needed by f826df95332c07380206dbd54178b6eefb311aba. In particular,
this tree lacks IOAM and several newer devconf fields and drop reasons.

Also annotate rpl_seg_enabled with READ_ONCE() and min(), and use swap()
for the existing RPL address exchange, eliminating its temporary address.
These changes supply the exact RPL context expected by the target without
adding functions or importing unrelated receive-path refactors. Keep the
existing SRv6 NULL check for the target to move to the common caller.

Remove the redundant second idev lookup in ipv6_rthdr_rcv() while adapting
the accept_source_route annotation. Use the already acquired RCU pointer.

Provide a macro local to the routing-header section mapping
kfree_skb_reason(skb, reason) to kfree_skb(skb). Linux 5.10 has no skb drop
reason API; this permits the unchanged target to build while retaining
this branch's existing packet-freeing semantics. No reason enum or new
function is introduced.

[ sashal: Reduced backport -- upstream 2f0ff05a44302 touches 7 file(s), this
  backport carries 1. Not backported here:
  net/ipv6/addrconf.c
  net/ipv6/ioam6.c
  net/ipv6/ip6_input.c
  net/ipv6/mcast.c
  net/ipv6/ndisc.c
  net/ipv6/seg6_hmac.c
  This note is generated from the file lists only; see the resolution record
  for the reasoning. ]

Stable-dep-of: f826df95332c ("ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/ipv6/exthdrs.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 0230fa98a3482..8099715a08a5d 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -368,9 +368,8 @@ static int ipv6_srh_rcv(struct sk_buff *skb)
 		return -1;
 	}
 
-	accept_seg6 = net->ipv6.devconf_all->seg6_enabled;
-	if (accept_seg6 > idev->cnf.seg6_enabled)
-		accept_seg6 = idev->cnf.seg6_enabled;
+	accept_seg6 = min(READ_ONCE(net->ipv6.devconf_all->seg6_enabled),
+			  READ_ONCE(idev->cnf.seg6_enabled));
 
 	if (!accept_seg6) {
 		kfree_skb(skb);
@@ -481,7 +480,6 @@ static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
 	struct net *net = dev_net(skb->dev);
 	struct inet6_dev *idev;
 	struct ipv6hdr *oldhdr;
-	struct in6_addr addr;
 	unsigned int chdr_len;
 	unsigned char *buf;
 	int accept_rpl_seg;
@@ -491,10 +489,8 @@ static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
 
 	idev = __in6_dev_get(skb->dev);
 
-	accept_rpl_seg = net->ipv6.devconf_all->rpl_seg_enabled;
-	if (accept_rpl_seg > idev->cnf.rpl_seg_enabled)
-		accept_rpl_seg = idev->cnf.rpl_seg_enabled;
-
+	accept_rpl_seg = min(READ_ONCE(net->ipv6.devconf_all->rpl_seg_enabled),
+			     READ_ONCE(idev->cnf.rpl_seg_enabled));
 	if (!accept_rpl_seg) {
 		kfree_skb(skb);
 		return -1;
@@ -593,9 +589,7 @@ static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
 		return -1;
 	}
 
-	addr = ipv6_hdr(skb)->daddr;
-	ipv6_hdr(skb)->daddr = ohdr->rpl_segaddr[i];
-	ohdr->rpl_segaddr[i] = addr;
+	swap(ipv6_hdr(skb)->daddr, ohdr->rpl_segaddr[i]);
 
 	ipv6_rpl_srh_compress(chdr, ohdr, &ipv6_hdr(skb)->daddr, n);
 
@@ -663,6 +657,9 @@ static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
   Routing header.
  ********************************/
 
+/* This stable tree has no skb drop-reason accounting. */
+#define kfree_skb_reason(skb, reason) kfree_skb(skb)
+
 /* called with rcu_read_lock() */
 static int ipv6_rthdr_rcv(struct sk_buff *skb)
 {
@@ -674,11 +671,13 @@ static int ipv6_rthdr_rcv(struct sk_buff *skb)
 	struct ipv6_rt_hdr *hdr;
 	struct rt0_hdr *rthdr;
 	struct net *net = dev_net(skb->dev);
-	int accept_source_route = net->ipv6.devconf_all->accept_source_route;
+	int accept_source_route;
 
-	idev = __in6_dev_get(skb->dev);
-	if (idev && accept_source_route > idev->cnf.accept_source_route)
-		accept_source_route = idev->cnf.accept_source_route;
+	accept_source_route = READ_ONCE(net->ipv6.devconf_all->accept_source_route);
+
+	if (idev)
+		accept_source_route = min(accept_source_route,
+					  READ_ONCE(idev->cnf.accept_source_route));
 
 	if (!pskb_may_pull(skb, skb_transport_offset(skb) + 8) ||
 	    !pskb_may_pull(skb, (skb_transport_offset(skb) +
@@ -858,6 +857,8 @@ static const struct inet6_protocol rthdr_protocol = {
 	.flags		=	INET6_PROTO_NOPOLICY,
 };
 
+#undef kfree_skb_reason
+
 static const struct inet6_protocol destopt_protocol = {
 	.handler	=	ipv6_destopt_rcv,
 	.flags		=	INET6_PROTO_NOPOLICY,
-- 
2.53.0

[PATCH 5.10.y 2/2] ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv()

[Sasha Levin]

From: Andrea Mayer <andrea.mayer@uniroma2.it>

[ Upstream commit f826df95332c07380206dbd54178b6eefb311aba ]

ipv6_rpl_srh_rcv() dereferences idev from __in6_dev_get() without a NULL
check when reading idev->cnf.rpl_seg_enabled.

When the device's MTU drops below IPV6_MIN_MTU, addrconf_ifdown() clears
dev->ip6_ptr through RCU_INIT_POINTER(). A packet that passed the idev
check in ip6_rcv_core() can then reach ipv6_rpl_srh_rcv() with
dev->ip6_ptr already NULL.

Reproduced by flooding the receiving interface with ping6 traffic while
flapping its MTU between 1500 and 1200:

 BUG: KASAN: null-ptr-deref in ipv6_rpl_srh_rcv+0xb3/0x1070
 Read of size 4 at addr 00000000000006b4 by task ping6/394

 CPU: 2 UID: 0 PID: 394 Comm: ping6 Not tainted 7.2.0-rc7-micro-vm-dev-00095-g24ef02f934ee #240 PREEMPT(full)
 Call Trace:
  <IRQ>
  kasan_report+0xc6/0x100
  ipv6_rpl_srh_rcv+0xb3/0x1070
  ip6_protocol_deliver_rcu+0x759/0x9a0
  ip6_input_finish+0xa8/0x1b0
  ip6_input+0xe1/0x490
  ipv6_rcv+0x33d/0x460
  __netif_receive_skb_one_core+0xd6/0x130
  process_backlog+0x2cc/0xa00
  __napi_poll.constprop.0+0x56/0x270
  net_rx_action+0x327/0x730
  handle_softirqs+0x11e/0x630
  do_softirq+0xb3/0xf0
  </IRQ>

Both ipv6_rpl_srh_rcv() and ipv6_srh_rcv() are called only from
ipv6_rthdr_rcv(), which already has an idev lookup.

Fix the NULL dereference on the RPL path by checking idev in
ipv6_rthdr_rcv(), before it calls either function. The callees take idev as
an argument and no longer call __in6_dev_get(), so the packet is now
dropped in one place, with SKB_DROP_REASON_IPV6DISABLED on both paths.

Fixes: 8610c7c6e3bd ("net: ipv6: add support for rpl sr exthdr")
Cc: stable@vger.kernel.org
Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Tested-by: Xiang Mei <xmei5@asu.edu>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260817132644.2223-1-andrea.mayer@uniroma2.it
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/ipv6/exthdrs.c | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 8099715a08a5d..83d2b6515aa41 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -351,23 +351,16 @@ static void seg6_update_csum(struct sk_buff *skb)
 			   (__be32 *)addr);
 }
 
-static int ipv6_srh_rcv(struct sk_buff *skb)
+static int ipv6_srh_rcv(struct sk_buff *skb, struct inet6_dev *idev)
 {
 	struct inet6_skb_parm *opt = IP6CB(skb);
 	struct net *net = dev_net(skb->dev);
 	struct ipv6_sr_hdr *hdr;
-	struct inet6_dev *idev;
 	struct in6_addr *addr;
 	int accept_seg6;
 
 	hdr = (struct ipv6_sr_hdr *)skb_transport_header(skb);
 
-	idev = __in6_dev_get(skb->dev);
-	if (!idev) {
-		kfree_skb(skb);
-		return -1;
-	}
-
 	accept_seg6 = min(READ_ONCE(net->ipv6.devconf_all->seg6_enabled),
 			  READ_ONCE(idev->cnf.seg6_enabled));
 
@@ -473,12 +466,11 @@ static int ipv6_srh_rcv(struct sk_buff *skb)
 	return -1;
 }
 
-static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
+static int ipv6_rpl_srh_rcv(struct sk_buff *skb, struct inet6_dev *idev)
 {
 	struct ipv6_rpl_sr_hdr *hdr, *ohdr, *chdr;
 	struct inet6_skb_parm *opt = IP6CB(skb);
 	struct net *net = dev_net(skb->dev);
-	struct inet6_dev *idev;
 	struct ipv6hdr *oldhdr;
 	unsigned int chdr_len;
 	unsigned char *buf;
@@ -487,8 +479,6 @@ static int ipv6_rpl_srh_rcv(struct sk_buff *skb)
 	u64 n = 0;
 	u32 r;
 
-	idev = __in6_dev_get(skb->dev);
-
 	accept_rpl_seg = min(READ_ONCE(net->ipv6.devconf_all->rpl_seg_enabled),
 			     READ_ONCE(idev->cnf.rpl_seg_enabled));
 	if (!accept_rpl_seg) {
@@ -699,10 +689,14 @@ static int ipv6_rthdr_rcv(struct sk_buff *skb)
 	switch (hdr->type) {
 	case IPV6_SRCRT_TYPE_4:
 		/* segment routing */
-		return ipv6_srh_rcv(skb);
+		if (!idev)
+			goto disabled;
+		return ipv6_srh_rcv(skb, idev);
 	case IPV6_SRCRT_TYPE_3:
 		/* rpl segment routing */
-		return ipv6_rpl_srh_rcv(skb);
+		if (!idev)
+			goto disabled;
+		return ipv6_rpl_srh_rcv(skb, idev);
 	default:
 		break;
 	}
@@ -850,6 +844,10 @@ static int ipv6_rthdr_rcv(struct sk_buff *skb)
 	icmpv6_param_prob(skb, ICMPV6_HDR_FIELD,
 			  (&hdr->type) - skb_network_header(skb));
 	return -1;
+
+disabled:
+	kfree_skb_reason(skb, SKB_DROP_REASON_IPV6DISABLED);
+	return -1;
 }
 
 static const struct inet6_protocol rthdr_protocol = {
-- 
2.53.0