[PATCH net] net: phonet: free phonet_device after RCU grace period

[PATCH net] net: phonet: free phonet_device after RCU grace period

[Santosh Kalluri]

phonet_device_destroy() removes a phonet_device from the per-net device
list with list_del_rcu(), but frees it immediately. RCU readers walking
the same list can still hold a pointer to the object after it has been
removed, leading to a slab-use-after-free.

Use kfree_rcu(), matching the lifetime rule already used by
phonet_address_del() for the same object type.

Fixes: eeb74a9d45f7 ("Phonet: convert devices list to RCU")
Cc: stable@vger.kernel.org
Signed-off-by: Santosh Kalluri <santosh.kalluri129@gmail.com>
Acked-by: Rémi Denis-Courmont <remi@remlab.net>
---
 net/phonet/pn_dev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/phonet/pn_dev.c b/net/phonet/pn_dev.c
index 86325b7fc1b6..ad44831d6745 100644
--- a/net/phonet/pn_dev.c
+++ b/net/phonet/pn_dev.c
@@ -108,7 +108,7 @@ static void phonet_device_destroy(struct net_device *dev)
 		for_each_set_bit(addr, pnd->addrs, 64)
 			phonet_address_notify(net, RTM_DELADDR, ifindex, addr);
 
-		kfree(pnd);
+		kfree_rcu(pnd, rcu);
 	}
 }
 

base-commit: f723ccaff2fb72b71ae8a9fd283f0dee4d9ae7a3
-- 
2.43.0

Re: [PATCH net] net: phonet: free phonet_device after RCU grace period

[Simon Horman]

On Wed, Jun 03, 2026 at 05:08:43PM -0700, Santosh Kalluri wrote:
> phonet_device_destroy() removes a phonet_device from the per-net device
> list with list_del_rcu(), but frees it immediately. RCU readers walking
> the same list can still hold a pointer to the object after it has been
> removed, leading to a slab-use-after-free.
> 
> Use kfree_rcu(), matching the lifetime rule already used by
> phonet_address_del() for the same object type.
> 
> Fixes: eeb74a9d45f7 ("Phonet: convert devices list to RCU")
> Cc: stable@vger.kernel.org
> Signed-off-by: Santosh Kalluri <santosh.kalluri129@gmail.com>
> Acked-by: Rémi Denis-Courmont <remi@remlab.net>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH net] net: phonet: free phonet_device after RCU grace period

[patchwork-bot+netdevbpf]

Hello:

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

On Wed,  3 Jun 2026 17:08:43 -0700 you wrote:
> phonet_device_destroy() removes a phonet_device from the per-net device
> list with list_del_rcu(), but frees it immediately. RCU readers walking
> the same list can still hold a pointer to the object after it has been
> removed, leading to a slab-use-after-free.
> 
> Use kfree_rcu(), matching the lifetime rule already used by
> phonet_address_del() for the same object type.
> 
> [...]

Here is the summary with links:
  - [net] net: phonet: free phonet_device after RCU grace period
    https://git.kernel.org/netdev/net/c/71de0177b28d

You are awesome, thank you!
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