From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9182E59B69B for ; Tue, 8 Sep 2026 22:37:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788907045; cv=none; b=oS4g/RpF1AGMBhv17jHrhVyXWD96Ckh5GGshj7wdipUGSr4wm2DY1F1bpD9ge0Bjcw80ETEcmsd5VhoZnUcwieGmb7MMoETqRUhagnXpZ1AJ2heqlk5YssBgN5yKCLbpjxxUGr056sHQoPEvTZviMvxXP90HjuAYG/kd1lIHhH0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788907045; c=relaxed/simple; bh=oyxEgOoM7H3g1YNpNo9R7UXMQLRfpIMLshD9ljvfe+E=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=t8FtaoJ98QcUlpEPWZ9B2ibdj31YRa3sSDmCAQc7rKRtj3PbsZnDBc1B5eUI4pyOEYte/mL2RCo34/ziz2598xWODUTUTfypO+U6PWAF15VM4xQ4EPP7zVkUUqbiyxOHsVFRQyEZZGGLRzG3AN7nGU+umiRSnTv3svjmd7NGGqo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=cUe/W/GU; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="cUe/W/GU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0C451F00ACF; Tue, 8 Sep 2026 22:37:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788907042; bh=cPc/tPElK0qfDWQSHNEiiq9tg5wABAo7h2w+PbZkVGE=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=cUe/W/GUX96ZryCOuzf+hrPc8o6xfPehCgcludpbRirgICuPH7a/0XSC9sspFCULM NWXhibTCjUb75OKGRBxLjEN6DlxViYjDia3Oox6KV2wGd9scClcAJp1NKpGg5vN4KX l8dKyffEX1jNTZci/VwJ2z7ylKI1GzAdaZf8tMmMAnKwsZ2umzruU0EJnvJNfETf7i 1TE58VLJoIrqFFtWhZH4ktBae1wjmgJdYRYs4eXCRVyKWG07TM0qB898G+T5JI6JwK Urmb9w6IpZRCB1h9DrFlhAK/1d5WVjGEVHlhqZiVrAGH/3oS5i2MhyStRPEDIuD1PU K9Vrtcqus8E6Q== From: Sasha Levin To: stable@vger.kernel.org Cc: Andrea Mayer , Xiang Mei , Simon Horman , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.15.y 3/3] ipv6: rpl: fix NULL dereference of idev in ipv6_rpl_srh_rcv() Date: Tue, 8 Sep 2026 18:37:18 -0400 Message-ID: <20260908223718.507924-3-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260908223718.507924-1-sashal@kernel.org> References: <2026090351-sagging-obliged-3e7b@gregkh> <20260908223718.507924-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Andrea Mayer [ 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: 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 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 Tested-by: Xiang Mei Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260817132644.2223-1-andrea.mayer@uniroma2.it Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- 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 1a9e2f989734c..8fb56237c771e 100644 --- a/net/ipv6/exthdrs.c +++ b/net/ipv6/exthdrs.c @@ -365,23 +365,16 @@ 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)); @@ -488,12 +481,11 @@ 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; @@ -503,8 +495,6 @@ 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) { @@ -715,10 +705,14 @@ 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; } @@ -866,6 +860,10 @@ 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