From patchwork Fri Jan 28 04:47:15 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Duoming Zhou X-Patchwork-Id: 12727929 X-Patchwork-Delegate: kuba@kernel.org 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 7E10CC433FE for ; Fri, 28 Jan 2022 04:55:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346133AbiA1Ezu (ORCPT ); Thu, 27 Jan 2022 23:55:50 -0500 Received: from mail.zju.edu.cn ([61.164.42.155]:40516 "EHLO zju.edu.cn" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1346148AbiA1EzU (ORCPT ); Thu, 27 Jan 2022 23:55:20 -0500 Received: from ubuntu.localdomain (unknown [10.15.192.164]) by mail-app2 (Coremail) with SMTP id by_KCgBHTIRXdfNhomB5AQ--.44160S3; Fri, 28 Jan 2022 12:47:25 +0800 (CST) From: Duoming Zhou To: linux-hams@vger.kernel.org Cc: jreuter@yaina.de, ralf@linux-mips.org, davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Duoming Zhou Subject: [PATCH 1/2] ax25: improve the incomplete fix to avoid UAF and NPD bugs Date: Fri, 28 Jan 2022 12:47:15 +0800 Message-Id: <87e509950a15e85274f902f29311f6234ee9f59f.1643343397.git.duoming@zju.edu.cn> X-Mailer: git-send-email 2.17.1 In-Reply-To: References: In-Reply-To: References: X-CM-TRANSID: by_KCgBHTIRXdfNhomB5AQ--.44160S3 X-Coremail-Antispam: 1UD129KBjvJXoW7AF1kZr18CF4kCFyktFy8Grg_yoW5JryrpF WUGF4FgFZrGF4Y9rsxGa97XF10vF4UK398Gr15Zan3u3s8JF95XFyktrWjq34YyrZ5JF18 ZasrK34fXw4jva7anT9S1TB71UUUUUDqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUka1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s1l1IIY67AE w4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2 IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVW8Jr0_Cr1UM28EF7xvwVC2 z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v26rxl6s0DM2AIxVAIcxkEcV Aq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r1Y 6r17McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64 vIr41lF7I21c0EjII2zVCS5cI20VAGYxC7MxAIw28IcxkI7VAKI48JMxAIw28IcVCjz48v 1sIEY20_GFWkJr1UJwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r 18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vI r41lIxAIcVC0I7IYx2IY67AKxVWUCVW8JwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr 1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r4j6F4UMIIF0xvE x4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUp6wZUUUUU= X-CM-SenderInfo: qssqjiasttq6lmxovvfxof0/ Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org The previous commit 1ade48d0c27d ("ax25: NPD bug when detaching AX25 device") introduce lock_sock() into ax25_kill_by_device to prevent NPD bug. But the concurrency NPD or UAF bug will occur, when lock_sock() or release_sock() dereferences the ax25_cb->sock. The NULL pointer dereference bug can be shown as below: ax25_kill_by_device() | ax25_release() | ax25_destroy_socket() | ax25_cb_del() ... | ... | ax25->sk=NULL; lock_sock(s->sk); //(1) | s->ax25_dev = NULL; | ... release_sock(s->sk); //(2) | ... | The root cause is that the sock is set to null before dereference site (1) or (2). Therefore, this patch extracts the ax25_cb->sock in advance, and uses ax25_list_lock to protect it, which can synchronize with ax25_cb_del() and ensure the value of sock is not null before dereference sites. The concurrency UAF bug can be shown as below: ax25_kill_by_device() | ax25_release() | ax25_destroy_socket() ... | ... | sock_put(sk); //FREE lock_sock(s->sk); //(1) | s->ax25_dev = NULL; | ... release_sock(s->sk); //(2) | ... | The root cause is that the sock is released before dereference site (1) or (2). Therefore, this patch uses sock_hold() to increase the refcount of sock and uses ax25_list_lock to protect it, which can synchronize with ax25_cb_del() in ax25_destroy_socket() and ensure the sock wil not be released before dereference sites. Signed-off-by: Duoming Zhou --- net/ax25/af_ax25.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 02f43f3e2c5..44a8730c26a 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -77,6 +77,7 @@ static void ax25_kill_by_device(struct net_device *dev) { ax25_dev *ax25_dev; ax25_cb *s; + struct sock *sk; if ((ax25_dev = ax25_dev_ax25dev(dev)) == NULL) return; @@ -85,13 +86,15 @@ static void ax25_kill_by_device(struct net_device *dev) again: ax25_for_each(s, &ax25_list) { if (s->ax25_dev == ax25_dev) { + sk = s->sk; + sock_hold(sk); spin_unlock_bh(&ax25_list_lock); - lock_sock(s->sk); + lock_sock(sk); s->ax25_dev = NULL; - release_sock(s->sk); + release_sock(sk); ax25_disconnect(s, ENETUNREACH); spin_lock_bh(&ax25_list_lock); - + sock_put(sk); /* The entry could have been deleted from the * list meanwhile and thus the next pointer is * no longer valid. Play it safe and restart From patchwork Fri Jan 28 04:47:16 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Duoming Zhou X-Patchwork-Id: 12727928 X-Patchwork-Delegate: kuba@kernel.org 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 65E1DC433F5 for ; Fri, 28 Jan 2022 04:55:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237388AbiA1Ezs (ORCPT ); Thu, 27 Jan 2022 23:55:48 -0500 Received: from mail.zju.edu.cn ([61.164.42.155]:40514 "EHLO zju.edu.cn" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1346147AbiA1EzU (ORCPT ); Thu, 27 Jan 2022 23:55:20 -0500 Received: from ubuntu.localdomain (unknown [10.15.192.164]) by mail-app2 (Coremail) with SMTP id by_KCgBHTIRXdfNhomB5AQ--.44160S4; Fri, 28 Jan 2022 12:47:26 +0800 (CST) From: Duoming Zhou To: linux-hams@vger.kernel.org Cc: jreuter@yaina.de, ralf@linux-mips.org, davem@davemloft.net, kuba@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Duoming Zhou Subject: [PATCH 2/2] ax25: add refcount in ax25_dev to avoid UAF bugs Date: Fri, 28 Jan 2022 12:47:16 +0800 Message-Id: <855641b37699b6ff501c4bae8370d26f59da9c81.1643343397.git.duoming@zju.edu.cn> X-Mailer: git-send-email 2.17.1 In-Reply-To: References: In-Reply-To: References: X-CM-TRANSID: by_KCgBHTIRXdfNhomB5AQ--.44160S4 X-Coremail-Antispam: 1UD129KBjvJXoW3AF4UWryxGFykGFyUKr1Dtrb_yoW7ur1rpF W0kayrArZ7tFy7Ars5Wr1xWF1jyryjq39rAr1UuF1Skw15J3s8JF18tryUKry7GrW3AF18 X34DXr4UAr48ZF7anT9S1TB71UUUUUDqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUka1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s1l1IIY67AE w4v_Jr0_Jr4l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xvwVC0I7IYx2 IY67AKxVWDJVCq3wA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVW8Jr0_Cr1UM28EF7xvwVC2 z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v26rxl6s0DM2AIxVAIcxkEcV Aq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r1Y 6r17McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IYc2Ij64 vIr41lF7I21c0EjII2zVCS5cI20VAGYxC7MxAIw28IcxkI7VAKI48JMxAIw28IcVCjz48v 1sIEY20_GFWkJr1UJwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s026c02F40E14v26r1j6r 18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vI r41lIxAIcVC0I7IYx2IY67AKxVWUCVW8JwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Gr0_Cr 1lIxAIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r4j6F4UMIIF0xvE x4A2jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x0JUp6wZUUUUU= X-CM-SenderInfo: qssqjiasttq6lmxovvfxof0/ Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org 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 --- 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(-) diff --git a/include/net/ax25.h b/include/net/ax25.h index 526e4958919..50b417df622 100644 --- a/include/net/ax25.h +++ b/include/net/ax25.h @@ -239,6 +239,7 @@ 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 { @@ -293,6 +294,15 @@ static __inline__ void ax25_cb_put(ax25_cb *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; diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 44a8730c26a..32f61978ff2 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -91,6 +91,7 @@ static void ax25_kill_by_device(struct net_device *dev) 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); @@ -439,6 +440,7 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg) } out_put: + ax25_dev_put(ax25_dev); ax25_cb_put(ax25); return ret; diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c index 256fadb94df..770b787fb7b 100644 --- a/net/ax25/ax25_dev.c +++ b/net/ax25/ax25_dev.c @@ -37,6 +37,7 @@ ax25_dev *ax25_addr_ax25dev(ax25_address *addr) for (ax25_dev = ax25_dev_list; ax25_dev != NULL; ax25_dev = ax25_dev->next) if (ax25cmp(addr, (const ax25_address *)ax25_dev->dev->dev_addr) == 0) { res = ax25_dev; + ax25_dev_hold(ax25_dev); } spin_unlock_bh(&ax25_dev_lock); @@ -56,6 +57,7 @@ void ax25_dev_device_up(struct net_device *dev) return; } + refcount_set(&ax25_dev->refcount, 1); dev->ax25_ptr = ax25_dev; ax25_dev->dev = dev; dev_hold_track(dev, &ax25_dev->dev_tracker, GFP_ATOMIC); @@ -83,6 +85,7 @@ void ax25_dev_device_up(struct net_device *dev) 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); @@ -112,20 +115,22 @@ void ax25_dev_device_down(struct net_device *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_track(dev, &ax25_dev->dev_tracker); - 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_track(dev, &ax25_dev->dev_tracker); - kfree(ax25_dev); + ax25_dev_put(ax25_dev); return; } @@ -133,6 +138,7 @@ void ax25_dev_device_down(struct net_device *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) @@ -149,6 +155,7 @@ int ax25_fwd_ioctl(unsigned int cmd, struct ax25_fwd_struct *fwd) if (ax25_dev->forward != NULL) return -EINVAL; ax25_dev->forward = fwd_dev->dev; + ax25_dev_put(fwd_dev); break; case SIOCAX25DELFWD: @@ -161,6 +168,7 @@ int ax25_fwd_ioctl(unsigned int cmd, struct ax25_fwd_struct *fwd) return -EINVAL; } + ax25_dev_put(ax25_dev); return 0; } diff --git a/net/ax25/ax25_route.c b/net/ax25/ax25_route.c index d0b2e094bd5..1e32693833e 100644 --- a/net/ax25/ax25_route.c +++ b/net/ax25/ax25_route.c @@ -116,6 +116,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route) 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); @@ -172,6 +173,7 @@ static int ax25_rt_del(struct ax25_routes_struct *route) } } } + ax25_dev_put(ax25_dev); write_unlock_bh(&ax25_route_lock); return 0; @@ -214,6 +216,7 @@ static int ax25_rt_opt(struct ax25_route_opt_struct *rt_option) } out: + ax25_dev_put(ax25_dev); write_unlock_bh(&ax25_route_lock); return err; }