[PATCH 5.4 52/67] ipv6: Fix nexthop refcnt leak when creating ipv6 route info

Greg Kroah-Hartman
2020-08-10T15:28:25Z

From: Xiyu Yang <xiyuyang19@fudan.edu.cn>

[ Upstream commit 706ec919164622ff5ce822065472d0f30a9e9dd2 ]

ip6_route_info_create() invokes nexthop_get(), which increases the
refcount of the "nh".

When ip6_route_info_create() returns, local variable "nh" becomes
invalid, so the refcount should be decreased to keep refcount balanced.

The reference counting issue happens in one exception handling path of
ip6_route_info_create(). When nexthops can not be used with source
routing, the function forgets to decrease the refcnt increased by
nexthop_get(), causing a refcnt leak.

Fix this issue by pulling up the error source routing handling when
nexthops can not be used with source routing.

Fixes: f88d8ea67fbd ("ipv6: Plumb support for nexthop object in a fib6_info")
Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@gmail.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/route.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3686,14 +3686,14 @@ static struct fib6_info *ip6_route_info_
rt->fib6_src.plen = cfg->fc_src_len;
#endif
if (nh) {
- if (!nexthop_get(nh)) {
- NL_SET_ERR_MSG(extack, "Nexthop has been deleted");
- goto out;
- }
if (rt->fib6_src.plen) {
NL_SET_ERR_MSG(extack, "Nexthops can not be used with source routing");
goto out;
}
+ if (!nexthop_get(nh)) {
+ NL_SET_ERR_MSG(extack, "Nexthop has been deleted");
+ goto out;
+ }
rt->nh = nh;
fib6_nh = nexthop_fib6_nh(rt->nh);
} else {