netdev - [PATCH] ipv6: ip6_fib: fix null-pointer dereference in ipv6_route_native_seq

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Message-ID: <CAH_kV5G07_ZL9O41OBYR8JrtxJsr56+Zi=65T_FkaQDefLU_DA@mail.gmail.com>
Date: Sun, 3 Nov 2024 04:33:10 +0800
From: Yi Zou <03zouyi09.25@...il.com>
To: Markus Elfring <Markus.Elfring@....de>
Cc: "David S. Miller" <davem@...emloft.net>, 21210240012@...udan.edu.cn, 
	21302010073@...udan.edu.cn, David Ahern <dsahern@...nel.org>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
	LKML <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org, 
	Paolo Abeni <pabeni@...hat.com>
Subject: [PATCH] ipv6: ip6_fib: fix null-pointer dereference in ipv6_route_native_seq_show()

Check if fib6_nh is non-NULL before accessing fib6_nh->fib_nh_gw_family
in ipv6_route_native_seq_show() to prevent a null-pointer dereference.
Assign dev as dev = fib6_nh ? fib6_nh->fib_nh_dev : NULL to ensure safe
handling when nexthop_fib6_nh(rt->nh) returns NULL.

Fixes: 0379e8e6a9ef ("ipv6: ip6_fib: avoid NPD in ipv6_route_native_seq_show()")

Signed-off-by: Yi Zou <03zouyi09.25@...il.com>
---
net/ipv6/ip6_fib.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index eb111d20615c..6632ab65d206 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -2555,14 +2555,14 @@ static int ipv6_route_native_seq_show(struct
seq_file *seq, void *v)
#else
seq_puts(seq, "00000000000000000000000000000000 00 ");
#endif
- if (fib6_nh->fib_nh_gw_family) {
+ if (fib6_nh && fib6_nh->fib_nh_gw_family) {
flags |= RTF_GATEWAY;
seq_printf(seq, "%pi6", &fib6_nh->fib_nh_gw6);
} else {
seq_puts(seq, "00000000000000000000000000000000");
}
- dev = fib6_nh->fib_nh_dev;
+ dev = fib6_nh ? fib6_nh->fib_nh_dev : NULL;
seq_printf(seq, " %08x %08x %08x %08x %8s\n",
rt->fib6_metric, refcount_read(&rt->fib6_ref), 0,
flags, dev ? dev->name : "");
--
2.44.0