From patchwork Wed Nov 10 23:00:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Todd Kjos X-Patchwork-Id: 12613527 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A407C433F5 for ; Wed, 10 Nov 2021 23:00:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 80AB56128B for ; Wed, 10 Nov 2021 23:00:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233979AbhKJXC4 (ORCPT ); Wed, 10 Nov 2021 18:02:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46244 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234026AbhKJXC4 (ORCPT ); Wed, 10 Nov 2021 18:02:56 -0500 Received: from mail-pj1-x104a.google.com (mail-pj1-x104a.google.com [IPv6:2607:f8b0:4864:20::104a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 092C6C0613F5 for ; Wed, 10 Nov 2021 15:00:08 -0800 (PST) Received: by mail-pj1-x104a.google.com with SMTP id x18-20020a17090a789200b001a7317f995cso2003319pjk.4 for ; Wed, 10 Nov 2021 15:00:08 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=NNtCs/5Asdgm6ZFGpEfa7ooseuLLQp0DNLVc8QA+Qxc=; b=nhsM5qNip0GWTl9WLxLWO7V0RpbBb3DBIwEXUFpkD8bnYnN5+ssWx72X1tjMx/FB70 Pbrlo9F3YwOPaIWGQ7mdUTMjeaXwxUvGKli9we7tCM8rn20LRx/C7bkrGiqPRgCSC/OT 4ixMSL2lX1R93/wddvuP+Vow7Ep2d91vRYRvrWypAQSOkzx4E/uoZubrqAceVibTbN87 cZl9jCnBh4PhjmAp8YbYLd/AOQX0Xl9fn1AcjMVZaxvTWab0jdm9emKpjBV6OGDK7dWv QmykrhmJ6dE3IC67Ddq9P7YSEkF461dxqnvDPTenO3G05XbTTwKjLSCKgM/77nJgS9TR OYgg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=NNtCs/5Asdgm6ZFGpEfa7ooseuLLQp0DNLVc8QA+Qxc=; b=FWNJPH4nIfEA6lqSuTGgiyPB+5HjnJrl2I6UfQXb2dbVnxUrZ6MwdslhDTsjV6JiiF Z+sgcd/55ORTWZT7T4K3dMdX6o9bmMSxCeiQMc+Gm40b91wdwE1IfUB3S9gK7bGp+OoO aT66r18mKY4qbMGB0jGtcLoia6Ix886Ag0iZSKKD+/Touq2JJcdtre2gHPiAT+tCvixe 7lyfaRaFrTt+PDY2YWM+ep+15ReP08ZY4wQBid5ZXbEyrmGnaGWrUL6dVJ0mmzgx1ptY FeAJKjDAUPEk56rc1UJPLSaO7ntnU6P9DjZBG3TBbUKddXcHRZ0RWuSKlueNXairPJUg kKHA== X-Gm-Message-State: AOAM531f6JTp5PifLJHcxBddvEzOcBMQELeIyIhk+Wk698WJ3lRH6dtw nw0eu+nQFeNUoYz/kIXUHyY8awHVUg== X-Google-Smtp-Source: ABdhPJzfmbvcdwiBN03d/zTSOvM+WMgFuMWfvsDrxxruIbYfM1j+IsSOPHJf8XD7UM0mYdGHjZn/SQr4hQ== X-Received: from tkjos-desktop.mtv.corp.google.com ([2620:15c:211:200:4a73:99b6:9694:8c4d]) (user=tkjos job=sendgmr) by 2002:a05:6a00:2391:b0:47c:2747:b1f5 with SMTP id f17-20020a056a00239100b0047c2747b1f5mr2682892pfc.44.1636585207324; Wed, 10 Nov 2021 15:00:07 -0800 (PST) Date: Wed, 10 Nov 2021 15:00:02 -0800 Message-Id: <20211110230003.3270335-1-tkjos@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.34.0.rc0.344.g81b53c2807-goog Subject: [PATCH 4.14 1/2] binder: use euid from cred instead of using task From: Todd Kjos To: stable@vger.kernel.org, gregkh@linuxfoundation.org, arve@android.com, tkjos@android.com, maco@android.com, christian@brauner.io, jmorris@namei.org, serge@hallyn.com, paul@paul-moore.com, stephen.smalley.work@gmail.com, eparis@parisplace.org, keescook@chromium.org, jannh@google.com, jeffv@google.com, zohar@linux.ibm.com, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, devel@driverdev.osuosl.org Cc: joel@joelfernandes.org, kernel-team@android.com, Todd Kjos , Casey Schaufler Precedence: bulk List-ID: commit 29bc22ac5e5bc63275e850f0c8fc549e3d0e306b upstream. Save the 'struct cred' associated with a binder process at initial open to avoid potential race conditions when converting to an euid. Set a transaction's sender_euid from the 'struct cred' saved at binder_open() instead of looking up the euid from the binder proc's 'struct task'. This ensures the euid is associated with the security context that of the task that opened binder. Cc: stable@vger.kernel.org # 4.4+ Fixes: 457b9a6f09f0 ("Staging: android: add binder driver") Signed-off-by: Todd Kjos Suggested-by: Stephen Smalley Suggested-by: Jann Horn Acked-by: Casey Schaufler Signed-off-by: Paul Moore Change-Id: I91922e7f359df5901749f1b09094c3c68d45aed4 --- drivers/android/binder.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 0db4b5646036..332b4a2cbb94 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -484,6 +484,9 @@ enum binder_deferred_state { * @files files_struct for process * (protected by @files_lock) * @files_lock mutex to protect @files + * @cred struct cred associated with the `struct file` + * in binder_open() + * (invariant after initialized) * @deferred_work_node: element for binder_deferred_list * (protected by binder_deferred_lock) * @deferred_work: bitmap of deferred work to perform @@ -532,6 +535,7 @@ struct binder_proc { struct task_struct *tsk; struct files_struct *files; struct mutex files_lock; + const struct cred *cred; struct hlist_node deferred_work_node; int deferred_work; bool is_dead; @@ -2890,7 +2894,7 @@ static void binder_transaction(struct binder_proc *proc, t->from = thread; else t->from = NULL; - t->sender_euid = task_euid(proc->tsk); + t->sender_euid = proc->cred->euid; t->to_proc = target_proc; t->to_thread = target_thread; t->code = tr->code; @@ -4261,6 +4265,7 @@ static void binder_free_proc(struct binder_proc *proc) BUG_ON(!list_empty(&proc->delivered_death)); binder_alloc_deferred_release(&proc->alloc); put_task_struct(proc->tsk); + put_cred(proc->cred); binder_stats_deleted(BINDER_STAT_PROC); kfree(proc); } @@ -4717,6 +4722,7 @@ static int binder_open(struct inode *nodp, struct file *filp) get_task_struct(current->group_leader); proc->tsk = current->group_leader; mutex_init(&proc->files_lock); + proc->cred = get_cred(filp->f_cred); INIT_LIST_HEAD(&proc->todo); proc->default_priority = task_nice(current); binder_dev = container_of(filp->private_data, struct binder_device, From patchwork Wed Nov 10 23:00:03 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Todd Kjos X-Patchwork-Id: 12613529 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 320C8C433F5 for ; Wed, 10 Nov 2021 23:00:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1CF0E61267 for ; Wed, 10 Nov 2021 23:00:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234100AbhKJXDF (ORCPT ); Wed, 10 Nov 2021 18:03:05 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46262 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234026AbhKJXC6 (ORCPT ); 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d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=nNSKuSyJlEq+LXpv5Vt3CW83FPMoywwo+7StO4wQnxs=; b=YDFBmmjlkvf3Ktpm7AibyXeqR1/BYn5TbKD8zgpAOw7v9MYo9lsuucqS34SBdV1Z32 gFh9y/m3hRYSssQ1ki9r6IzbvRqk4nxGZBN1msfW5i/JmudGjiuvOj6VS8D4athDsXkD VmPZC/CEeT0z92w87hO7g9KEPpXBTCKOAmH1B47HpGgjKVGk4HHXrukZo0weZf6dkL3w 4rGBkDhMyYmSRTiXVEI/IpT/GvHt3sR7BJZBLomLfXTJqh8ynxl+dukr9Gk90s/Sf1mm TEbwgwa6+mhgiv7AjWUAkCnqTYWTvfivWul207+hZ0FGXB85QLxM/PAklwywy7H36f44 JZpg== X-Gm-Message-State: AOAM533qTKEHjOhD0vb4/Z0h/RRrNKjAAs1+mnnQEJAN4kNRYzmp2D2d TsHkEXF4wHXbB/aGsi/BEye9MXO0RA== X-Google-Smtp-Source: ABdhPJzh5oPYDCvAEVQsRbCbfxskas3705YxxemVS6fPVdXzDb62HhX49ADP79cQ4vcv25Uaiv0AE5I/QQ== X-Received: from tkjos-desktop.mtv.corp.google.com ([2620:15c:211:200:4a73:99b6:9694:8c4d]) (user=tkjos job=sendgmr) by 2002:a25:ae1a:: with SMTP id a26mr3192549ybj.70.1636585209690; Wed, 10 Nov 2021 15:00:09 -0800 (PST) Date: Wed, 10 Nov 2021 15:00:03 -0800 In-Reply-To: <20211110230003.3270335-1-tkjos@google.com> Message-Id: <20211110230003.3270335-2-tkjos@google.com> Mime-Version: 1.0 References: <20211110230003.3270335-1-tkjos@google.com> X-Mailer: git-send-email 2.34.0.rc0.344.g81b53c2807-goog Subject: [PATCH 4.14 2/2] binder: use cred instead of task for selinux checks From: Todd Kjos To: stable@vger.kernel.org, gregkh@linuxfoundation.org, arve@android.com, tkjos@android.com, maco@android.com, christian@brauner.io, jmorris@namei.org, serge@hallyn.com, paul@paul-moore.com, stephen.smalley.work@gmail.com, eparis@parisplace.org, keescook@chromium.org, jannh@google.com, jeffv@google.com, zohar@linux.ibm.com, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, devel@driverdev.osuosl.org Cc: joel@joelfernandes.org, kernel-team@android.com, Todd Kjos , Casey Schaufler Precedence: bulk List-ID: commit 52f88693378a58094c538662ba652aff0253c4fe upstream. Since binder was integrated with selinux, it has passed 'struct task_struct' associated with the binder_proc to represent the source and target of transactions. The conversion of task to SID was then done in the hook implementations. It turns out that there are race conditions which can result in an incorrect security context being used. Fix by using the 'struct cred' saved during binder_open and pass it to the selinux subsystem. Cc: stable@vger.kernel.org # 5.14 (need backport for earlier stables) Fixes: 79af73079d75 ("Add security hooks to binder and implement the hooks for SELinux.") Suggested-by: Jann Horn Signed-off-by: Todd Kjos Acked-by: Casey Schaufler Signed-off-by: Paul Moore Change-Id: Id7157515d2b08f11683aeb8ad9b8f1da075d34e7 --- drivers/android/binder.c | 12 ++++++------ include/linux/lsm_hooks.h | 28 ++++++++++++++-------------- include/linux/security.h | 28 ++++++++++++++-------------- security/security.c | 14 +++++++------- security/selinux/hooks.c | 31 +++++++++++++------------------ 5 files changed, 54 insertions(+), 59 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 332b4a2cbb94..c5fd7908fc91 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2285,7 +2285,7 @@ static int binder_translate_binder(struct flat_binder_object *fp, ret = -EINVAL; goto done; } - if (security_binder_transfer_binder(proc->tsk, target_proc->tsk)) { + if (security_binder_transfer_binder(proc->cred, target_proc->cred)) { ret = -EPERM; goto done; } @@ -2331,7 +2331,7 @@ static int binder_translate_handle(struct flat_binder_object *fp, proc->pid, thread->pid, fp->handle); return -EINVAL; } - if (security_binder_transfer_binder(proc->tsk, target_proc->tsk)) { + if (security_binder_transfer_binder(proc->cred, target_proc->cred)) { ret = -EPERM; goto done; } @@ -2415,7 +2415,7 @@ static int binder_translate_fd(int fd, ret = -EBADF; goto err_fget; } - ret = security_binder_transfer_file(proc->tsk, target_proc->tsk, file); + ret = security_binder_transfer_file(proc->cred, target_proc->cred, file); if (ret < 0) { ret = -EPERM; goto err_security; @@ -2802,8 +2802,8 @@ static void binder_transaction(struct binder_proc *proc, return_error_line = __LINE__; goto err_invalid_target_handle; } - if (security_binder_transaction(proc->tsk, - target_proc->tsk) < 0) { + if (security_binder_transaction(proc->cred, + target_proc->cred) < 0) { return_error = BR_FAILED_REPLY; return_error_param = -EPERM; return_error_line = __LINE__; @@ -4469,7 +4469,7 @@ static int binder_ioctl_set_ctx_mgr(struct file *filp) ret = -EBUSY; goto out; } - ret = security_binder_set_context_mgr(proc->tsk); + ret = security_binder_set_context_mgr(proc->cred); if (ret < 0) goto out; if (uid_valid(context->binder_context_mgr_uid)) { diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index c9258124e417..569debc49f3d 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -1170,22 +1170,22 @@ * * @binder_set_context_mgr: * Check whether @mgr is allowed to be the binder context manager. - * @mgr contains the task_struct for the task being registered. + * @mgr contains the struct cred for the current binder process. * Return 0 if permission is granted. * @binder_transaction: * Check whether @from is allowed to invoke a binder transaction call * to @to. - * @from contains the task_struct for the sending task. - * @to contains the task_struct for the receiving task. + * @from contains the struct cred for the sending process. + * @to contains the struct cred for the receiving process. * @binder_transfer_binder: * Check whether @from is allowed to transfer a binder reference to @to. - * @from contains the task_struct for the sending task. - * @to contains the task_struct for the receiving task. + * @from contains the struct cred for the sending process. + * @to contains the struct cred for the receiving process. * @binder_transfer_file: * Check whether @from is allowed to transfer @file to @to. - * @from contains the task_struct for the sending task. + * @from contains the struct cred for the sending process. * @file contains the struct file being transferred. - * @to contains the task_struct for the receiving task. + * @to contains the struct cred for the receiving process. * * @ptrace_access_check: * Check permission before allowing the current process to trace the @@ -1353,13 +1353,13 @@ * @ctxlen points to the place to put the length of @ctx. */ union security_list_options { - int (*binder_set_context_mgr)(struct task_struct *mgr); - int (*binder_transaction)(struct task_struct *from, - struct task_struct *to); - int (*binder_transfer_binder)(struct task_struct *from, - struct task_struct *to); - int (*binder_transfer_file)(struct task_struct *from, - struct task_struct *to, + int (*binder_set_context_mgr)(const struct cred *mgr); + int (*binder_transaction)(const struct cred *from, + const struct cred *to); + int (*binder_transfer_binder)(const struct cred *from, + const struct cred *to); + int (*binder_transfer_file)(const struct cred *from, + const struct cred *to, struct file *file); int (*ptrace_access_check)(struct task_struct *child, diff --git a/include/linux/security.h b/include/linux/security.h index dab093af4ee8..1c8968a267c2 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -197,13 +197,13 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts) extern int security_init(void); /* Security operations */ -int security_binder_set_context_mgr(struct task_struct *mgr); -int security_binder_transaction(struct task_struct *from, - struct task_struct *to); -int security_binder_transfer_binder(struct task_struct *from, - struct task_struct *to); -int security_binder_transfer_file(struct task_struct *from, - struct task_struct *to, struct file *file); +int security_binder_set_context_mgr(const struct cred *mgr); +int security_binder_transaction(const struct cred *from, + const struct cred *to); +int security_binder_transfer_binder(const struct cred *from, + const struct cred *to); +int security_binder_transfer_file(const struct cred *from, + const struct cred *to, struct file *file); int security_ptrace_access_check(struct task_struct *child, unsigned int mode); int security_ptrace_traceme(struct task_struct *parent); int security_capget(struct task_struct *target, @@ -424,25 +424,25 @@ static inline int security_init(void) return 0; } -static inline int security_binder_set_context_mgr(struct task_struct *mgr) +static inline int security_binder_set_context_mgr(const struct cred *mgr) { return 0; } -static inline int security_binder_transaction(struct task_struct *from, - struct task_struct *to) +static inline int security_binder_transaction(const struct cred *from, + const struct cred *to) { return 0; } -static inline int security_binder_transfer_binder(struct task_struct *from, - struct task_struct *to) +static inline int security_binder_transfer_binder(const struct cred *from, + const struct cred *to) { return 0; } -static inline int security_binder_transfer_file(struct task_struct *from, - struct task_struct *to, +static inline int security_binder_transfer_file(const struct cred *from, + const struct cred *to, struct file *file) { return 0; diff --git a/security/security.c b/security/security.c index 4fbe4e495c02..737a5985343c 100644 --- a/security/security.c +++ b/security/security.c @@ -222,25 +222,25 @@ EXPORT_SYMBOL(unregister_lsm_notifier); /* Security operations */ -int security_binder_set_context_mgr(struct task_struct *mgr) +int security_binder_set_context_mgr(const struct cred *mgr) { return call_int_hook(binder_set_context_mgr, 0, mgr); } -int security_binder_transaction(struct task_struct *from, - struct task_struct *to) +int security_binder_transaction(const struct cred *from, + const struct cred *to) { return call_int_hook(binder_transaction, 0, from, to); } -int security_binder_transfer_binder(struct task_struct *from, - struct task_struct *to) +int security_binder_transfer_binder(const struct cred *from, + const struct cred *to) { return call_int_hook(binder_transfer_binder, 0, from, to); } -int security_binder_transfer_file(struct task_struct *from, - struct task_struct *to, struct file *file) +int security_binder_transfer_file(const struct cred *from, + const struct cred *to, struct file *file) { return call_int_hook(binder_transfer_file, 0, from, to, file); } diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 895d369bc410..9bb1d492f704 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2136,21 +2136,18 @@ static inline u32 open_file_to_av(struct file *file) /* Hook functions begin here. */ -static int selinux_binder_set_context_mgr(struct task_struct *mgr) +static int selinux_binder_set_context_mgr(const struct cred *mgr) { - u32 mysid = current_sid(); - u32 mgrsid = task_sid(mgr); - - return avc_has_perm(mysid, mgrsid, SECCLASS_BINDER, + return avc_has_perm(current_sid(), cred_sid(mgr), SECCLASS_BINDER, BINDER__SET_CONTEXT_MGR, NULL); } -static int selinux_binder_transaction(struct task_struct *from, - struct task_struct *to) +static int selinux_binder_transaction(const struct cred *from, + const struct cred *to) { u32 mysid = current_sid(); - u32 fromsid = task_sid(from); - u32 tosid = task_sid(to); + u32 fromsid = cred_sid(from); + u32 tosid = cred_sid(to); int rc; if (mysid != fromsid) { @@ -2164,21 +2161,19 @@ static int selinux_binder_transaction(struct task_struct *from, NULL); } -static int selinux_binder_transfer_binder(struct task_struct *from, - struct task_struct *to) +static int selinux_binder_transfer_binder(const struct cred *from, + const struct cred *to) { - u32 fromsid = task_sid(from); - u32 tosid = task_sid(to); - - return avc_has_perm(fromsid, tosid, SECCLASS_BINDER, BINDER__TRANSFER, + return avc_has_perm(cred_sid(from), cred_sid(to), + SECCLASS_BINDER, BINDER__TRANSFER, NULL); } -static int selinux_binder_transfer_file(struct task_struct *from, - struct task_struct *to, +static int selinux_binder_transfer_file(const struct cred *from, + const struct cred *to, struct file *file) { - u32 sid = task_sid(to); + u32 sid = cred_sid(to); struct file_security_struct *fsec = file->f_security; struct dentry *dentry = file->f_path.dentry; struct inode_security_struct *isec;