[PATCH 6.12.y] ipv6: add NULL checks for idev in SRv6 paths

[PATCH 6.12.y] ipv6: add NULL checks for idev in SRv6 paths

[Li hongliang]

From: Minhong He <heminhong@kylinos.cn>

[ Upstream commit 06413793526251870e20402c39930804f14d59c0 ]

__in6_dev_get() can return NULL when the device has no IPv6 configuration
(e.g. MTU < IPV6_MIN_MTU or after NETDEV_UNREGISTER).

Add NULL checks for idev returned by __in6_dev_get() in both
seg6_hmac_validate_skb() and ipv6_srh_rcv() to prevent potential NULL
pointer dereferences.

Fixes: 1ababeba4a21 ("ipv6: implement dataplane support for rthdr type 4 (Segment Routing Header)")
Fixes: bf355b8d2c30 ("ipv6: sr: add core files for SR HMAC support")
Signed-off-by: Minhong He <heminhong@kylinos.cn>
Reviewed-by: Andrea Mayer <andrea.mayer@uniroma2.it>
Link: https://patch.msgid.link/20260316073301.106643-1-heminhong@kylinos.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Li hongliang <1468888505@139.com>
---
 net/ipv6/exthdrs.c   | 4 ++++
 net/ipv6/seg6_hmac.c | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 1a627c24e4c3..8a30dd83cf0b 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -379,6 +379,10 @@ static int ipv6_srh_rcv(struct sk_buff *skb)
 	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));
diff --git a/net/ipv6/seg6_hmac.c b/net/ipv6/seg6_hmac.c
index 5d21a74c1165..214d137d545e 100644
--- a/net/ipv6/seg6_hmac.c
+++ b/net/ipv6/seg6_hmac.c
@@ -245,6 +245,8 @@ bool seg6_hmac_validate_skb(struct sk_buff *skb)
 	int require_hmac;
 
 	idev = __in6_dev_get(skb->dev);
+	if (!idev)
+		return false;
 
 	srh = (struct ipv6_sr_hdr *)skb_transport_header(skb);
 
-- 
2.34.1