commit 92f1655aa2b2294d0b49925f3b875a634bd3b59e upstream.
__dst_negative_advice() does not enforce proper RCU rules when
sk->dst_cache must be cleared, leading to possible UAF.
RCU rules are that we must first clear sk->sk_dst_cache,
then call dst_release(old_dst).
Note that sk_dst_reset(sk) is implementing this protocol correctly,
while __dst_negative_advice() uses the wrong order.
Given that ip6_negative_advice() has special logic
against RTF_CACHE, this means each of the three ->negative_advice()
existing methods must perform the sk_dst_reset() themselves.
Note the check against NULL dst is centralized in
__dst_negative_advice(), there is no need to duplicate
it in various callbacks.
Many thanks to Clement Lecigne for tracking this issue.
This old bug became visible after the blamed commit, using UDP sockets.
Fixes: a87cb3e48ee8 ("net: Facility to report route quality of connected sockets")
Reported-by: Clement Lecigne <clecigne@google.com>
Diagnosed-by: Clement Lecigne <clecigne@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <tom@herbertland.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20240528114353.1794151-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[Lee: Stable backport]
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@vger.kernel.org # 5.4+
Fixes: 67f695134703 ("ipv6: Move setting default metric for routes")
Co-developed-by: Fan Yu <fan.yu9@zte.com.cn>
Signed-off-by: Fan Yu <fan.yu9@zte.com.cn>
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20240514201102055dD2Ba45qKbLlUMxu_DTHP@zte.com.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Eric Dumazet