5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: xu xin <xu.xin16@xxxxxxxxxx>
commit bb487272380d120295e955ad8acfcbb281b57642 upstream.
Problem
=========
After commit 67f695134703 ("ipv6: Move setting default metric for routes"),
we noticed that the logic of assigning the default value of fc_metirc
changed in the ioctl process. That is, when users use ioctl(fd, SIOCADDRT,
rt) with a non-zero metric to add a route, then they may fail to delete a
route with passing in a metric value of 0 to the kernel by ioctl(fd,
SIOCDELRT, rt). But iproute can succeed in deleting it.
As a reference, when using iproute tools by netlink to delete routes with
a metric parameter equals 0, like the command as follows:
ip -6 route del fe80::/64 via fe81::5054:ff:fe11:3451 dev eth0 metric 0
the user can still succeed in deleting the route entry with the smallest
metric.
Root Reason
===========
After commit 67f695134703 ("ipv6: Move setting default metric for routes"),
When ioctl() pass in SIOCDELRT with a zero metric, rtmsg_to_fib6_config()
will set a defalut value (1024) to cfg->fc_metric in kernel, and in
ip6_route_del() and the line 4074 at net/ipv3/route.c, it will check by
if (cfg->fc_metric && cfg->fc_metric != rt->fib6_metric)
continue;
and the condition is true and skip the later procedure (deleting route)
because cfg->fc_metric != rt->fib6_metric. But before that commit,
cfg->fc_metric is still zero there, so the condition is false and it
will do the following procedure (deleting).
Solution
========
In order to keep a consistent behaviour across netlink() and ioctl(), we
should allow to delete a route with a metric value of 0. So we only do
the default setting of fc_metric in route adding.
CC: stable@xxxxxxxxxxxxxxx # 5.4+
Fixes: 67f695134703 ("ipv6: Move setting default metric for routes")
Co-developed-by: Fan Yu <fan.yu9@xxxxxxxxxx>
Signed-off-by: Fan Yu <fan.yu9@xxxxxxxxxx>
Signed-off-by: xu xin <xu.xin16@xxxxxxxxxx>
Reviewed-by: David Ahern <dsahern@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240514201102055dD2Ba45qKbLlUMxu_DTHP@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv6/route.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -4341,7 +4341,7 @@ static void rtmsg_to_fib6_config(struct
.fc_table = l3mdev_fib_table_by_index(net, rtmsg->rtmsg_ifindex) ?
: RT6_TABLE_MAIN,
.fc_ifindex = rtmsg->rtmsg_ifindex,
- .fc_metric = rtmsg->rtmsg_metric ? : IP6_RT_PRIO_USER,
+ .fc_metric = rtmsg->rtmsg_metric,
.fc_expires = rtmsg->rtmsg_info,
.fc_dst_len = rtmsg->rtmsg_dst_len,
.fc_src_len = rtmsg->rtmsg_src_len,
@@ -4377,6 +4377,9 @@ int ipv6_route_ioctl(struct net *net, un
rtnl_lock();
switch (cmd) {
case SIOCADDRT:
+ /* Only do the default setting of fc_metric in route adding */
+ if (cfg.fc_metric == 0)
+ cfg.fc_metric = IP6_RT_PRIO_USER;
err = ip6_route_add(&cfg, GFP_KERNEL, NULL);
break;
case SIOCDELRT:
