From patchwork Wed Nov 10 23:00:24 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Todd Kjos X-Patchwork-Id: 12613537 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 90D3AC43217 for ; Wed, 10 Nov 2021 23:00:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 779916128B for ; Wed, 10 Nov 2021 23:00:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234104AbhKJXDU (ORCPT ); Wed, 10 Nov 2021 18:03:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46376 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234057AbhKJXDT (ORCPT ); Wed, 10 Nov 2021 18:03:19 -0500 Received: from mail-qk1-x74a.google.com (mail-qk1-x74a.google.com [IPv6:2607:f8b0:4864:20::74a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B1424C061767 for ; Wed, 10 Nov 2021 15:00:31 -0800 (PST) Received: by mail-qk1-x74a.google.com with SMTP id s20-20020a05620a0bd400b0045e893f2ed8so2913649qki.11 for ; Wed, 10 Nov 2021 15:00:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=AyO5APv0B3j2lJDIzBcNaAzCnbUGVx9ja7WSxNT1cAM=; b=DhZFjR36Sqw40TdNkE8v7w057R1mfkXgVdIrPyDbxX11V9LcQcuBUPZ29VnmeAKKpX QqQa0FHgX9XgKWBP6UJe55VEQ4TxR7JtvUWmueGH9LWrdelmApfHjI5ZmpR6hEV2hlP8 eDlnkcXq25wz4EMaP0f+El8TDuV7zyAjPGxz1aaxaoVxippGkuwT9j2LPDhQ+wwN404c oa1b2Vb6+AAMjSQPX6vkFOms2ql8In2ksLD4cypPP9tKj3W7R4alKk+s3n//zBps/UoN sA73gIqq9R7xQekjjO/QrIxQ5GNtwxzJFJAuukKBMUuveJkLJJM0n2O76OaqfZ2rnz6G lEWA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=AyO5APv0B3j2lJDIzBcNaAzCnbUGVx9ja7WSxNT1cAM=; b=fYm5MRspxT1PebsDDeoYXOd8mZHOA6AemHI+Fm8IFXsSThB6aRNRwr9SADlgrtIteO yoZtDoEgovpEUVVsHPf9xl4IkoHMlZl9YnV866Tfnk2sEXXnNeUl+9Vb4T9Ixmw3J/nJ R8VyVKZC1SpcbRfhQlxv3mbIr0mSjccoaQpRnmAcuo+a6AkEtUkDA4OErSG862v9K9tQ hYSkQNqIDOR9//4FF3LGEfL8sQr8n3M3aXb1ekTgmBqI0/11MDahfDktFk4WsntiEHzC qT9EFPdbJQTwMmhowBP9Q9MY33mZ0n/USlHv1wjGEajXRlnLo987jJRy+5eboW5MiZRJ g7Zw== X-Gm-Message-State: AOAM533xD9xaTYO3SI8ILVUc4MWKfJPryM1coGGhuvn9APQwh0vEAh6O CkpZpJoC8SKvV5oZpsZRS0cw0vlhZw== X-Google-Smtp-Source: ABdhPJxSWLLHSq6+0QpnuL6EWkgcfAhSLc8NVZ78+KSA6O//hOneGnzz90C5uL+A6Oa7SCObhv99ElfsMg== X-Received: from tkjos-desktop.mtv.corp.google.com ([2620:15c:211:200:4a73:99b6:9694:8c4d]) (user=tkjos job=sendgmr) by 2002:ac8:5fc5:: with SMTP id k5mr2988581qta.110.1636585230768; Wed, 10 Nov 2021 15:00:30 -0800 (PST) Date: Wed, 10 Nov 2021 15:00:24 -0800 In-Reply-To: <20211110230025.3272776-1-tkjos@google.com> Message-Id: <20211110230025.3272776-2-tkjos@google.com> Mime-Version: 1.0 References: <20211110230025.3272776-1-tkjos@google.com> X-Mailer: git-send-email 2.34.0.rc0.344.g81b53c2807-goog Subject: [PATCH 5.4 2/3] 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 | 36 +++++++++++++++--------------------- 5 files changed, 56 insertions(+), 62 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 64f6fb3b1f66..cebb2cd1876c 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2447,7 +2447,7 @@ 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; } @@ -2493,7 +2493,7 @@ 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; } @@ -2581,7 +2581,7 @@ static int binder_translate_fd(u32 fd, binder_size_t fd_offset, 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; @@ -2980,8 +2980,8 @@ 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__; @@ -4922,7 +4922,7 @@ 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 a3763247547c..a21dc5413653 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -1241,22 +1241,22 @@ * * @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 @@ -1456,13 +1456,13 @@ * @what: kernel feature being accessed */ 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 df90399a8af9..0d4cb64cae1f 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -249,13 +249,13 @@ extern int security_init(void); extern int early_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, @@ -481,25 +481,25 @@ static inline int early_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 1bc000f834e2..c34ec4c7d98c 100644 --- a/security/security.c +++ b/security/security.c @@ -670,25 +670,25 @@ static void __init lsm_early_task(struct task_struct *task) /* 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 717a398ef4d0..8b9cbe1e8ee2 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -2050,22 +2050,19 @@ 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(&selinux_state, - mysid, mgrsid, SECCLASS_BINDER, + 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) { @@ -2076,27 +2073,24 @@ static int selinux_binder_transaction(struct task_struct *from, return rc; } - return avc_has_perm(&selinux_state, - fromsid, tosid, SECCLASS_BINDER, BINDER__CALL, - NULL); + return avc_has_perm(&selinux_state, fromsid, tosid, + SECCLASS_BINDER, BINDER__CALL, 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(&selinux_state, - fromsid, tosid, SECCLASS_BINDER, BINDER__TRANSFER, + 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 = selinux_file(file); struct dentry *dentry = file->f_path.dentry; struct inode_security_struct *isec;