6.12-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit f8d8ce1b515a0a6af72b30502670a406cfb75073 ]
fib6_info_uses_dev() seems to rely on RCU without an explicit protection.
Like the prior fix in rt6_nlmsg_size(), we need to make sure fib6_del_route() or fib6_add_rt2node() have not removed the anchor from the list, or we risk an infinite loop.
Fixes: d9ccb18f83ea ("ipv6: Fix soft lockups in fib6_select_path under high next hop churn") Signed-off-by: Eric Dumazet edumazet@google.com Link: https://patch.msgid.link/20250725140725.3626540-4-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/ipv6/route.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c index f1e64c1cc49b..8b84ed926cd1 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -5875,16 +5875,21 @@ static bool fib6_info_uses_dev(const struct fib6_info *f6i, if (f6i->fib6_nh->fib_nh_dev == dev) return true;
- if (f6i->fib6_nsiblings) { - struct fib6_info *sibling, *next_sibling; + if (READ_ONCE(f6i->fib6_nsiblings)) { + const struct fib6_info *sibling;
- list_for_each_entry_safe(sibling, next_sibling, - &f6i->fib6_siblings, fib6_siblings) { - if (sibling->fib6_nh->fib_nh_dev == dev) + rcu_read_lock(); + list_for_each_entry_rcu(sibling, &f6i->fib6_siblings, + fib6_siblings) { + if (sibling->fib6_nh->fib_nh_dev == dev) { + rcu_read_unlock(); return true; + } + if (!READ_ONCE(f6i->fib6_nsiblings)) + break; } + rcu_read_unlock(); } - return false; }