[PATCH 5.10 331/491] ipv6: prevent possible UaF in addrconf_permanent_addr()

Greg Kroah-Hartman
2026-04-13T16:56:53Z

From: Paolo Abeni <pabeni@redhat.com>

[ Upstream commit fd63f185979b047fb22a0dfc6bd94d0cab6a6a70 ]

The mentioned helper try to warn the user about an exceptional
condition, but the message is delivered too late, accessing the ipv6
after its possible deletion.

Reorder the statement to avoid the possible UaF; while at it, place the
warning outside the idev->lock as it needs no protection.

Reported-by: Jakub Kicinski <kuba@kernel.org>
Closes: https://sashiko.dev/#/patchset/8c8bfe2e1a324e501f0e15fef404a77443fd8caf.1774365668.git.pabeni%40redhat.com
Fixes: f1705ec197e7 ("net: ipv6: Make address flushing on ifdown optional")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Link: https://patch.msgid.link/ef973c3a8cb4f8f1787ed469f3e5391b9fe95aa0.1774601542.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/addrconf.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index ced20abf4ef8e..758cea239e618 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3509,12 +3509,12 @@ static void addrconf_permanent_addr(struct net *net, struct net_device *dev)
if ((ifp->flags & IFA_F_PERMANENT) &&
fixup_permanent_addr(net, idev, ifp) < 0) {
write_unlock_bh(&idev->lock);
- in6_ifa_hold(ifp);
- ipv6_del_addr(ifp);
- write_lock_bh(&idev->lock);

net_info_ratelimited("%s: Failed to add prefix route for address %pI6c; dropping\n",
idev->dev->name, &ifp->addr);
+ in6_ifa_hold(ifp);
+ ipv6_del_addr(ifp);
+ write_lock_bh(&idev->lock);
}
}

--
2.53.0