ipv6: Fix dst leak for uncached routes.

ip6_route_output_flags(), ip6_rt_put_flags(), and ip6_dst_check()
detect an uncached route by list_empty(&rt->dst.rt_uncached),
which replaced the static DST_NOCACHE flag check in commit
a4c2fd7f7891 ("net: remove DST_NOCACHE flag").

When a device is unregistered, rt6_uncached_list_flush_dev()
unlinks uncached routes tied to the device from rt6_uncached_list.

Previously, they were moved to another list with list_move()
(__list_del_entry() + list_add()), and since commit 98aa546af5e4
("inet: remove (struct uncached_list)->quarantine"), the routes
are just unlinked with list_del_init().

If list_del_init() runs concurrently, list_empty() evaluates to
true; ip6_route_output_flags() calls dst_hold_safe() incorrectly
and ip6_rt_put_flags() skips ip6_rt_put(), leaking dst, and thus
dev tied via rt->from as well.

The same race is partially fixed by commit 9a6f0c4d5796 ("dst:
fix races in rt6_uncached_list_del() and rt_del_uncached_list()").

Let's check rt6->dst.rt_uncached_list instead.

Note that IPv4 does not have the same issue.

Fixes: 98aa546af5e4 ("inet: remove (struct uncached_list)->quarantine")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Hangbin Liu <liuhangbin@kylinos.cn>
Reviewed-by: Xuanqiang Luo <luoxuanqiang@kylinos.cn>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260920191558.2990636-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions