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Thu, 17 Sep 2026 23:09:06 -0700 (PDT) From: Adarsh Das To: gregkh@linuxfoundation.org Cc: rafael@kernel.org, dakr@kernel.org, driver-core@lists.linux.dev, stable@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+4393dfdddf166f2de2b0@syzkaller.appspotmail.com, Adarsh Das Subject: [PATCH v3] kobject: fix uevent socket use-after-free on net namespace delete Date: Fri, 18 Sep 2026 11:38:26 +0530 Message-ID: <20260918060826.8434-1-adarshdas950@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <2026091732-armored-lilac-fec9@gregkh> References: <2026091732-armored-lilac-fec9@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit When a network namespace is deleted, we free its uevent socket. But sometimes a device in that namespace is still being removed and tries to send a uevent through that socket. The socket is already freed, so KASAN reports a use-after-free. This patch attempts the fix of taking a lock around both the send path and the free path, and clear the pointer before freeing so nobody uses it after free. Reported-by: syzbot Link: https://syzkaller.appspot.com/bug?extid=4393dfdddf166f2de2b0 Tested-by: syzbot Tested-by: Adarsh Das Assisted-by: LLM Signed-off-by: Adarsh Das --- lib/kobject_uevent.c | 27 +++++++++++++++++++-------- 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c index ddbc4d7482d2..cb674c2c3432 100644 --- a/lib/kobject_uevent.c +++ b/lib/kobject_uevent.c @@ -13,6 +13,7 @@ * Greg Kroah-Hartman */ +#include #include #include #include @@ -411,9 +412,14 @@ static int kobject_uevent_net_broadcast(struct kobject *kobj, devpath); else { const struct net *net = container_of(ns, struct net, ns); - - ret = uevent_net_broadcast_tagged(net->uevent_sock->sk, env, - action_string, devpath); + struct uevent_sock *ue_sk; + + guard(mutex)(&uevent_sock_mutex); + ue_sk = net->uevent_sock; + if (ue_sk && ue_sk->sk) + ret = uevent_net_broadcast_tagged(ue_sk->sk, env, + action_string, + devpath); } #endif @@ -804,14 +810,19 @@ static int uevent_net_init(struct net *net) static void uevent_net_exit(struct net *net) { - struct uevent_sock *ue_sk = net->uevent_sock; + struct uevent_sock *ue_sk; - if (sock_net(ue_sk->sk)->user_ns == &init_user_ns) { - mutex_lock(&uevent_sock_mutex); - list_del(&ue_sk->list); - mutex_unlock(&uevent_sock_mutex); + { + guard(mutex)(&uevent_sock_mutex); + ue_sk = net->uevent_sock; + net->uevent_sock = NULL; + if (ue_sk && sock_net(ue_sk->sk)->user_ns == &init_user_ns) + list_del(&ue_sk->list); } + if (!ue_sk) + return; + netlink_kernel_release(ue_sk->sk); kfree(ue_sk); } -- 2.55.0