From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F246A24E4C3; Thu, 2 Jul 2026 16:55:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783011353; cv=none; b=RvLUpF7V8EwSIrN6KfH6gXb95SkQzQK2bvqP8S3X0KjmhFnfZQTa6puavwIqzeZ1uefjNyuqH94XrqD6SLEf/9l7Qt8pZLlcH7GeNUikhl07VQLGbe3kfz0dglucMmIIqrUcBwiOZ1OhY69FgzLwz8dJUzXDB8NNNuliuM9+n68= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783011353; c=relaxed/simple; bh=lI+jdOmwH6GbtMGup+0t+IBSJ5wHI5mtV9F6xkx2SGU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=REiQ8y2Em0Wc/e1a3DHNiOOa3YSuudkGoiTuLfiJSj7A0x7stSuDbNWTgm4fy3UsafZDdPdbYt02yxCNu1GhHZ4VpQBI2xwqxGetQg8TQ1PjW8jntgQLGj8ryeD6BnvIOM//idMqdjMLYndp+nh1md0nALBSJqwoHtWoaUXxIYI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=g2X8OI1Y; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="g2X8OI1Y" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 654431F000E9; Thu, 2 Jul 2026 16:55:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1783011351; bh=GG8KO5Wql8yIcT733jCxPBc/qbacvENa+42VzcNy/bA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=g2X8OI1YLArMycYpOrtxWXPBgIx0Yi5OLfc76+Adx4X2y32Gp2wvg91upNaQF1I6j /WJN5YNchkUCXspqpS7ih1VrWLkXlXjOAf1QB7V8dF7fI+kv28eWnCln5ComLnJy5D 6fz9b3JdXq61UEGfYFJsDt8+8R/6XoTDIvQpoC30= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Fan Wu , Jakub Kicinski Subject: [PATCH 6.18 076/108] hdlc_ppp: sync per-proto timers before freeing hdlc state Date: Thu, 2 Jul 2026 18:21:13 +0200 Message-ID: <20260702155113.687997420@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260702155112.110058792@linuxfoundation.org> References: <20260702155112.110058792@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Fan Wu commit c78a4e41ab5ead6193ad8a2dd92e8906bae659fa upstream. Each PPP control protocol (LCP/IPCP/IPV6CP) embedded in struct ppp registers a timer via timer_setup(). That struct ppp is the hdlc->state allocation, which detach_hdlc_protocol() frees with kfree() in both teardown paths: unregister_hdlc_device() and the re-attach inside attach_hdlc_protocol(). The ppp proto never registered a .detach callback, so detach_hdlc_protocol() performs no timer synchronization before the kfree(). The only cancel, timer_delete(&proto->timer) in ppp_cp_event(), is partial (it does not wait for a running callback) and only runs on the ->CLOSED transition; ppp_stop()/ppp_close() do not sync either. A ppp_timer callback already executing (blocked on ppp->lock) survives the kfree and then dereferences proto->state / ppp->lock in freed memory, leading to a use-after-free. Fix this by adding a .detach helper that calls timer_shutdown_sync() on every per-proto timer. detach_hdlc_protocol() invokes proto->detach(dev) before kfree(hdlc->state), so timer_shutdown_sync() now runs on both free paths. timer_shutdown_sync() is used instead of timer_delete_sync() because the keepalive path re-arms the timer through add_timer()/mod_timer() and shutdown blocks any re-activation during teardown. Initialize the per-protocol timers in ppp_ioctl() when the protocol is attached, and remove the now-redundant timer_setup() from ppp_start(), so that the timers are initialized exactly once at attach time and ppp_timer_release() never operates on uninitialized timer_list structures. attach_hdlc_protocol() uses kmalloc() (not kzalloc), so struct ppp's protos[i].timer is uninitialized garbage until the first timer_setup(); without this init-at-attach, attaching the PPP protocol without ever bringing the device up would leave timer_shutdown_sync() operating on uninitialized memory in .detach. Moving the init out of ppp_start() (which only runs on NETDEV_UP) into the attach path makes the initialization unconditional and avoids initializing the same timer_list twice. This bug was found by static analysis. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Fan Wu Link: https://patch.msgid.link/20260617020518.116319-1-fanwu01@zju.edu.cn Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- drivers/net/wan/hdlc_ppp.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) --- a/drivers/net/wan/hdlc_ppp.c +++ b/drivers/net/wan/hdlc_ppp.c @@ -621,7 +621,6 @@ static void ppp_start(struct net_device struct proto *proto = &ppp->protos[i]; proto->dev = dev; - timer_setup(&proto->timer, ppp_timer, 0); proto->state = CLOSED; } ppp->protos[IDX_LCP].pid = PID_LCP; @@ -641,6 +640,15 @@ static void ppp_close(struct net_device ppp_tx_flush(); } +static void ppp_timer_release(struct net_device *dev) +{ + struct ppp *ppp = get_ppp(dev); + int i; + + for (i = 0; i < IDX_COUNT; i++) + timer_shutdown_sync(&ppp->protos[i].timer); +} + static struct hdlc_proto proto = { .start = ppp_start, .stop = ppp_stop, @@ -649,6 +657,7 @@ static struct hdlc_proto proto = { .ioctl = ppp_ioctl, .netif_rx = ppp_rx, .module = THIS_MODULE, + .detach = ppp_timer_release, }; static const struct header_ops ppp_header_ops = { @@ -659,7 +668,7 @@ static int ppp_ioctl(struct net_device * { hdlc_device *hdlc = dev_to_hdlc(dev); struct ppp *ppp; - int result; + int i, result; switch (ifs->type) { case IF_GET_PROTO: @@ -687,6 +696,8 @@ static int ppp_ioctl(struct net_device * return result; ppp = get_ppp(dev); + for (i = 0; i < IDX_COUNT; i++) + timer_setup(&ppp->protos[i].timer, ppp_timer, 0); spin_lock_init(&ppp->lock); ppp->req_timeout = 2; ppp->cr_retries = 10;