From 6930d048efe7be06cd36e7413914be0bec4a45b5 Mon Sep 17 00:00:00 2001
From: Denys Fedoryshchenko <denys.f@collabora.com>
Date: Mon, 6 Jul 2026 11:04:10 +0300
Subject: ipoe: Fix OOPS if ipv6.disable=1

ipoe_recv() handles every ETH_P_IPV6 frame arriving on an IPoE
by calling ipoe_lookup_rt6()/ip6_route_output().
On ipv6.disable=1 IPv6 FIB is not initialized.
We can detect that by ipv6_mod_enabled() since kernel 4.8,
and return RX_HANDLER_PASS, so packet falls thru normal stack and get discarded.

Fixes: https://github.com/accel-ppp/accel-ppp/issues/313

Signed-off-by: Denys Fedoryshchenko <denys.f@collabora.com>
---
 drivers/ipoe/ipoe.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/ipoe/ipoe.c b/drivers/ipoe/ipoe.c
index 4050011f..2829e6ac 100644
--- a/drivers/ipoe/ipoe.c
+++ b/drivers/ipoe/ipoe.c
@@ -15,6 +15,7 @@
 #include <linux/init.h>
 #include <linux/if_ether.h>
 #include <linux/if_vlan.h>
+#include <linux/ipv6.h>
 #include <linux/semaphore.h>
 #include <linux/netfilter_ipv4.h>
 #include <linux/u64_stats_sync.h>
@@ -61,6 +62,14 @@
 #define RHEL_MAJOR 0
 #endif
 
+/* ipv6.disable=1 leaves the IPv6 FIB uninitialized, so ip6_route_output()
+ * oopses; ipv6_mod_enabled() detects that (and CONFIG_IPV6=n) since 4.8 */
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4,8,0)
+#define ipoe_ipv6_enabled() ipv6_mod_enabled()
+#else
+#define ipoe_ipv6_enabled() 1
+#endif
+
 static inline void ipoe_flowi4_set_tos(struct flowi4 *fl4, __u8 dsfield)
 {
 #ifdef flowi4_dscp
@@ -890,6 +899,9 @@ static rx_handler_result_t ipoe_recv(struct sk_buff **pskb)
 			return RX_HANDLER_CONSUMED;
 		}
 	} else if (skb->protocol == htons(ETH_P_IPV6)) {
+		if (!ipoe_ipv6_enabled())
+			return RX_HANDLER_PASS;
+
 		if (!pskb_may_pull(skb, sizeof(*ip6h) + noff))
 			return RX_HANDLER_PASS;
 
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