[PATCH net] ipv6: prevent possible UaF in addrconf_permanent_addr()

[PATCH net] ipv6: prevent possible UaF in addrconf_permanent_addr()

[Paolo Abeni]

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>
---
 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 f4e23b543585..dd0b4d80e0f8 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3625,12 +3625,12 @@ 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

Re: [PATCH net] ipv6: prevent possible UaF in addrconf_permanent_addr()

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Fri, 27 Mar 2026 10:52:57 +0100 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [net] ipv6: prevent possible UaF in addrconf_permanent_addr()
    https://git.kernel.org/netdev/net/c/fd63f185979b

You are awesome, thank you!
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