From patchwork Tue Apr 26 08:21:17 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "gregkh@linuxfoundation.org" X-Patchwork-Id: 566693 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF51BC433EF for ; Tue, 26 Apr 2022 08:33:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345020AbiDZIgN (ORCPT ); Tue, 26 Apr 2022 04:36:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345090AbiDZIeE (ORCPT ); Tue, 26 Apr 2022 04:34:04 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5B3C56A02B; Tue, 26 Apr 2022 01:25:59 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 1D2D7B81CF5; Tue, 26 Apr 2022 08:25:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74CCEC385AC; Tue, 26 Apr 2022 08:25:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1650961556; bh=hQQJexZ4MpOJ5d+Pv/RnkJ5TuHvqDFbTbbPUzM6su/Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=N6Hlj63Kb19kWYO86cjgJx3Nass0YQBn9gQbF/UODNKnHd9VW7qIcsROKAZkZlkKC 8E5DIVUEIiYw8F2u3RQeseTXvv1arrUm2yTZ/XqJfzvrV6uZaeeR4+ebTVqGgGn3u6 e8/lVR0nsRM2w8ZWMbR6YeSaELkLhwF1P+jKavAc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , Duoming Zhou , "David S. Miller" , Ovidiu Panait Subject: [PATCH 4.14 35/43] ax25: add refcount in ax25_dev to avoid UAF bugs Date: Tue, 26 Apr 2022 10:21:17 +0200 Message-Id: <20220426081735.550901087@linuxfoundation.org> X-Mailer: git-send-email 2.36.0 In-Reply-To: <20220426081734.509314186@linuxfoundation.org> References: <20220426081734.509314186@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Duoming Zhou commit d01ffb9eee4af165d83b08dd73ebdf9fe94a519b upstream. If we dereference ax25_dev after we call kfree(ax25_dev) in ax25_dev_device_down(), it will lead to concurrency UAF bugs. There are eight syscall functions suffer from UAF bugs, include ax25_bind(), ax25_release(), ax25_connect(), ax25_ioctl(), ax25_getname(), ax25_sendmsg(), ax25_getsockopt() and ax25_info_show(). One of the concurrency UAF can be shown as below: (USE) | (FREE) | ax25_device_event | ax25_dev_device_down ax25_bind | ... ... | kfree(ax25_dev) ax25_fillin_cb() | ... ax25_fillin_cb_from_dev() | ... | The root cause of UAF bugs is that kfree(ax25_dev) in ax25_dev_device_down() is not protected by any locks. When ax25_dev, which there are still pointers point to, is released, the concurrency UAF bug will happen. This patch introduces refcount into ax25_dev in order to guarantee that there are no pointers point to it when ax25_dev is released. Signed-off-by: Duoming Zhou Signed-off-by: David S. Miller [OP: backport to 4.14: adjusted context] Signed-off-by: Ovidiu Panait Signed-off-by: Greg Kroah-Hartman --- include/net/ax25.h | 10 ++++++++++ net/ax25/af_ax25.c | 2 ++ net/ax25/ax25_dev.c | 12 ++++++++++-- net/ax25/ax25_route.c | 3 +++ 4 files changed, 25 insertions(+), 2 deletions(-) --- a/include/net/ax25.h +++ b/include/net/ax25.h @@ -235,6 +235,7 @@ typedef struct ax25_dev { #if defined(CONFIG_AX25_DAMA_SLAVE) || defined(CONFIG_AX25_DAMA_MASTER) ax25_dama_info dama; #endif + refcount_t refcount; } ax25_dev; typedef struct ax25_cb { @@ -289,6 +290,15 @@ static __inline__ void ax25_cb_put(ax25_ } } +#define ax25_dev_hold(__ax25_dev) \ + refcount_inc(&((__ax25_dev)->refcount)) + +static __inline__ void ax25_dev_put(ax25_dev *ax25_dev) +{ + if (refcount_dec_and_test(&ax25_dev->refcount)) { + kfree(ax25_dev); + } +} static inline __be16 ax25_type_trans(struct sk_buff *skb, struct net_device *dev) { skb->dev = dev; --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -101,6 +101,7 @@ again: spin_unlock_bh(&ax25_list_lock); lock_sock(sk); s->ax25_dev = NULL; + ax25_dev_put(ax25_dev); release_sock(sk); ax25_disconnect(s, ENETUNREACH); spin_lock_bh(&ax25_list_lock); @@ -450,6 +451,7 @@ static int ax25_ctl_ioctl(const unsigned } out_put: + ax25_dev_put(ax25_dev); ax25_cb_put(ax25); return ret; --- a/net/ax25/ax25_dev.c +++ b/net/ax25/ax25_dev.c @@ -40,6 +40,7 @@ ax25_dev *ax25_addr_ax25dev(ax25_address for (ax25_dev = ax25_dev_list; ax25_dev != NULL; ax25_dev = ax25_dev->next) if (ax25cmp(addr, (ax25_address *)ax25_dev->dev->dev_addr) == 0) { res = ax25_dev; + ax25_dev_hold(ax25_dev); } spin_unlock_bh(&ax25_dev_lock); @@ -59,6 +60,7 @@ void ax25_dev_device_up(struct net_devic return; } + refcount_set(&ax25_dev->refcount, 1); dev->ax25_ptr = ax25_dev; ax25_dev->dev = dev; dev_hold(dev); @@ -86,6 +88,7 @@ void ax25_dev_device_up(struct net_devic spin_lock_bh(&ax25_dev_lock); ax25_dev->next = ax25_dev_list; ax25_dev_list = ax25_dev; + ax25_dev_hold(ax25_dev); spin_unlock_bh(&ax25_dev_lock); ax25_register_dev_sysctl(ax25_dev); @@ -115,20 +118,22 @@ void ax25_dev_device_down(struct net_dev if ((s = ax25_dev_list) == ax25_dev) { ax25_dev_list = s->next; + ax25_dev_put(ax25_dev); spin_unlock_bh(&ax25_dev_lock); dev->ax25_ptr = NULL; dev_put(dev); - kfree(ax25_dev); + ax25_dev_put(ax25_dev); return; } while (s != NULL && s->next != NULL) { if (s->next == ax25_dev) { s->next = ax25_dev->next; + ax25_dev_put(ax25_dev); spin_unlock_bh(&ax25_dev_lock); dev->ax25_ptr = NULL; dev_put(dev); - kfree(ax25_dev); + ax25_dev_put(ax25_dev); return; } @@ -136,6 +141,7 @@ void ax25_dev_device_down(struct net_dev } spin_unlock_bh(&ax25_dev_lock); dev->ax25_ptr = NULL; + ax25_dev_put(ax25_dev); } int ax25_fwd_ioctl(unsigned int cmd, struct ax25_fwd_struct *fwd) @@ -152,6 +158,7 @@ int ax25_fwd_ioctl(unsigned int cmd, str if (ax25_dev->forward != NULL) return -EINVAL; ax25_dev->forward = fwd_dev->dev; + ax25_dev_put(fwd_dev); break; case SIOCAX25DELFWD: @@ -164,6 +171,7 @@ int ax25_fwd_ioctl(unsigned int cmd, str return -EINVAL; } + ax25_dev_put(ax25_dev); return 0; } --- a/net/ax25/ax25_route.c +++ b/net/ax25/ax25_route.c @@ -119,6 +119,7 @@ static int __must_check ax25_rt_add(stru ax25_rt->dev = ax25_dev->dev; ax25_rt->digipeat = NULL; ax25_rt->ip_mode = ' '; + ax25_dev_put(ax25_dev); if (route->digi_count != 0) { if ((ax25_rt->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) { write_unlock_bh(&ax25_route_lock); @@ -175,6 +176,7 @@ static int ax25_rt_del(struct ax25_route } } } + ax25_dev_put(ax25_dev); write_unlock_bh(&ax25_route_lock); return 0; @@ -217,6 +219,7 @@ static int ax25_rt_opt(struct ax25_route } out: + ax25_dev_put(ax25_dev); write_unlock_bh(&ax25_route_lock); return err; }