[PATCH] ipv6: ip6_fib: fix null-pointer dereference in ipv6_route_native_seq_show()

[PATCH] ipv6: ip6_fib: fix null-pointer dereference in ipv6_route_native_seq_show()

[Yi Zou]

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@gmail.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

Re: [PATCH v4?] ipv6: ip6_fib: fix null-pointer dereference in ipv6_route_native_seq_show()

[Markus Elfring]

> 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.
…
> ---
> net/ipv6/ip6_fib.c | 4 ++--
…

It would have been more appropriate to add also a patch version description.

See also:
* https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.12-rc5#n321

* https://lore.kernel.org/all/?q=%22This+looks+like+a+new+version+of+a+previously+submitted+patch%22


Regards,
Markus