From patchwork Tue Oct 12 16:56:12 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Todd Kjos X-Patchwork-Id: 12553243 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 465E2C43219 for ; Tue, 12 Oct 2021 16:56:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2429D604DC for ; Tue, 12 Oct 2021 16:56:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231859AbhJLQ61 (ORCPT ); Tue, 12 Oct 2021 12:58:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37134 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231946AbhJLQ6Y (ORCPT ); Tue, 12 Oct 2021 12:58:24 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D805C061746 for ; Tue, 12 Oct 2021 09:56:22 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id x15-20020a056902102f00b005ba71cd7dbfso17721305ybt.8 for ; Tue, 12 Oct 2021 09:56:22 -0700 (PDT) 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=Mwae8Ejzsmbhdp150195SP11OIoOnZHvR8wRYQamjXg=; b=RZ/VZBHl1HvOJwMNfn/wyOhkRQ7x7ZEERi3vIgiH1zWADtTrwOSu3msb+uBQ5z/+zo 3SRgiJvV5Bx+HU9qQk24SooKq+aeGWwJss5ZPBHS18wTHIs5bVhCRZepq/qdObdMRKhb L1wunp82irR9mtPFWffaUV6KsDXII0nGdD20NleN0KqbzWVC0208pZOT4d+D6JotJ37o UPIzghFGIDn7oYQl0tpPAzhBjUOcRPP9Kw9hiNXU/AnPuXDgVwQKx2bRncxoSta3kYEd Vx9wTcnVuNVEYNH+hD6dM+xkjcqPgRqRdXv15pXgw/bjcpW3pwF2Tj7rlUe6rXYhVq4a 10uw== 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=Mwae8Ejzsmbhdp150195SP11OIoOnZHvR8wRYQamjXg=; b=xkhRRhrYQe9/Gb/BpJfX7hRtXrK60G6HZu+XXFs7JhjudY8Ou4nwvoyqbood9sb5H1 T6u433nCbU7tLFzoePQs5RjO8g5tbm6xxJbcknclRSUgtVNQ0SHKLlk0XWERPhKiJNJX 35fGZU2mAfAarMXQdE4Y7gsVJwXMgvnpAe/jjQ52z4Ofh1nmZnWDzcIzrkaREOlsHHO+ 43gGvTMj4Q0WTqhA0cT7BeLsVaskuHPu0zV9ubD/23UiDbA3sonUGvG876cPnxFFP31i cJC6OrY4FX/jhAjryu4l6VdPiKAjHMmOTYUVnAMyZdfAU9xAeQHKkXoFH0QPyWgMz0Lu EnTg== X-Gm-Message-State: AOAM530mM/KsOm2A5XtMDESVzYpJuJvE2biNPx1ipnrfIvj9ScAt9J7I LP2gNryA4A1dr3REFwOPDjHRWpfY6g== X-Google-Smtp-Source: ABdhPJzyTWT16jc0uAEpzHgNTjY8P3Cae43hy5GOBsxaWT1o4sIRwdkN+OAgexPrM9Wj0PqxVQ4ruuYa6g== X-Received: from ava-linux2.mtv.corp.google.com ([2620:15c:211:200:39c7:8168:c0b2:b46e]) (user=tkjos job=sendgmr) by 2002:a25:d94d:: with SMTP id q74mr29250835ybg.196.1634057781619; Tue, 12 Oct 2021 09:56:21 -0700 (PDT) Date: Tue, 12 Oct 2021 09:56:12 -0700 In-Reply-To: <20211012165614.2873369-1-tkjos@google.com> Message-Id: <20211012165614.2873369-2-tkjos@google.com> Mime-Version: 1.0 References: <20211012165614.2873369-1-tkjos@google.com> X-Mailer: git-send-email 2.33.0.882.g93a45727a2-goog Subject: [PATCH v5 1/3] binder: use euid from cred instead of using task From: Todd Kjos To: 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, linux-kernel@vger.kernel.org Cc: joel@joelfernandes.org, kernel-team@android.com, Todd Kjos , stable@vger.kernel.org Precedence: bulk List-ID: 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. Fixes: 457b9a6f09f0 ("Staging: android: add binder driver") Signed-off-by: Todd Kjos Suggested-by: Stephen Smalley Suggested-by: Jann Horn Cc: stable@vger.kernel.org # 4.4+ --- v3: added this patch to series (as 3/3) v5: - combined with saving of 'struct cred' during binder_open() - reordered to 1/1 as suggested by Stephen Smalley drivers/android/binder.c | 4 +++- drivers/android/binder_internal.h | 4 ++++ 2 files changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index 9edacc8b9768..a396015e874a 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2711,7 +2711,7 @@ 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; @@ -4353,6 +4353,7 @@ static void binder_free_proc(struct binder_proc *proc) } binder_alloc_deferred_release(&proc->alloc); put_task_struct(proc->tsk); + put_cred(proc->cred); binder_stats_deleted(BINDER_STAT_PROC); kfree(proc); } @@ -5055,6 +5056,7 @@ static int binder_open(struct inode *nodp, struct file *filp) spin_lock_init(&proc->outer_lock); get_task_struct(current->group_leader); proc->tsk = current->group_leader; + proc->cred = get_cred(filp->f_cred); INIT_LIST_HEAD(&proc->todo); init_waitqueue_head(&proc->freeze_wait); proc->default_priority = task_nice(current); diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h index 402c4d4362a8..d6b6b8cb7346 100644 --- a/drivers/android/binder_internal.h +++ b/drivers/android/binder_internal.h @@ -364,6 +364,9 @@ struct binder_ref { * (invariant after initialized) * @tsk task_struct for group_leader of process * (invariant after initialized) + * @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 @@ -426,6 +429,7 @@ struct binder_proc { struct list_head waiting_threads; int pid; struct task_struct *tsk; + const struct cred *cred; struct hlist_node deferred_work_node; int deferred_work; int outstanding_txns; From patchwork Tue Oct 12 16:56:13 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Todd Kjos X-Patchwork-Id: 12553245 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 47CE9C433EF for ; Tue, 12 Oct 2021 16:56:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 28A85604DC for ; Tue, 12 Oct 2021 16:56:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232260AbhJLQ6i (ORCPT ); Tue, 12 Oct 2021 12:58:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37166 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232072AbhJLQ6b (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=BsLbDcAOIwMHGIsnq8aLUA9IJSzH+U5i0yd822SC3S8=; b=gPAdxPeYF4EUpruKQIghfuB7i/K8pu6oyzzgBcJKP54U051UFUyC/waOh5yLwAhOJr /krQZuKXcQAdXDLNuiyPsr2mgNo0je0TuETZ73PWLqU9i9nmku9xG7yljF+S0/cOhhWh sMA9kZTSpiDVNXgPQ9GsfDpMkeOm52zWvpUPOHTSWtMw4H5vatdXYQSQz8FUQK4Rmace JNI4d/R96giVtqPPGMDYSWORGEndkM4wJluNZnP29ozTp8vLwQr1TFVknzn2575wX2OG x8zFEARHrgroDBXbv9fBVsQcb3DFKDOzMEhkhYn5FaV6WY+NlnA422+WTQ25b0Qe/urn 0Tqw== X-Gm-Message-State: AOAM533muzAfkR6Rh0W/cXizPydmR8Tf++tuKv4rwFjsasMP/K4XXlH9 at1pvXM5KQGc1Qa5mZpD9xF+gJkArQ== X-Google-Smtp-Source: ABdhPJxYlsUrPFKhrLgxOtm8cE3jcW3guEiUJrPT9qbvxm69br6P+/fXTyw1UUhHHfq46NWim1CuRbE3PA== X-Received: from ava-linux2.mtv.corp.google.com ([2620:15c:211:200:39c7:8168:c0b2:b46e]) (user=tkjos job=sendgmr) by 2002:a25:c644:: with SMTP id k65mr20833673ybf.191.1634057783946; Tue, 12 Oct 2021 09:56:23 -0700 (PDT) Date: Tue, 12 Oct 2021 09:56:13 -0700 In-Reply-To: <20211012165614.2873369-1-tkjos@google.com> Message-Id: <20211012165614.2873369-3-tkjos@google.com> Mime-Version: 1.0 References: <20211012165614.2873369-1-tkjos@google.com> X-Mailer: git-send-email 2.33.0.882.g93a45727a2-goog Subject: [PATCH v5 2/3] binder: use cred instead of task for selinux checks From: Todd Kjos To: 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, linux-kernel@vger.kernel.org Cc: joel@joelfernandes.org, kernel-team@android.com, Todd Kjos , stable@vger.kernel.org Precedence: bulk List-ID: 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. Fixes: 79af73079d75 ("Add security hooks to binder and implement the hooks for SELinux.") Suggested-by: Jann Horn Signed-off-by: Todd Kjos Cc: stable@vger.kernel.org # 5.14 (need backport for earlier stables) --- v2: updated comments as suggested by Paul Moore v3: added 2 patches to fix related issues v5: moved 'struct cred' save during binder_open() to patch 1/3 drivers/android/binder.c | 12 ++++----- include/linux/lsm_hook_defs.h | 14 +++++----- include/linux/lsm_hooks.h | 14 +++++----- include/linux/security.h | 28 ++++++++++---------- security/security.c | 14 +++++----- security/selinux/hooks.c | 48 ++++++++++------------------------- 6 files changed, 54 insertions(+), 76 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index a396015e874a..bc15325f0579 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2056,7 +2056,7 @@ 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; } @@ -2102,7 +2102,7 @@ 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; } @@ -2190,7 +2190,7 @@ 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; @@ -2595,8 +2595,8 @@ 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__; @@ -4565,7 +4565,7 @@ 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_hook_defs.h b/include/linux/lsm_hook_defs.h index 2adeea44c0d5..61590c1f2d33 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -26,13 +26,13 @@ * #undef LSM_HOOK * }; */ -LSM_HOOK(int, 0, binder_set_context_mgr, struct task_struct *mgr) -LSM_HOOK(int, 0, binder_transaction, struct task_struct *from, - struct task_struct *to) -LSM_HOOK(int, 0, binder_transfer_binder, struct task_struct *from, - struct task_struct *to) -LSM_HOOK(int, 0, binder_transfer_file, struct task_struct *from, - struct task_struct *to, struct file *file) +LSM_HOOK(int, 0, binder_set_context_mgr, const struct cred *mgr) +LSM_HOOK(int, 0, binder_transaction, const struct cred *from, + const struct cred *to) +LSM_HOOK(int, 0, binder_transfer_binder, const struct cred *from, + const struct cred *to) +LSM_HOOK(int, 0, binder_transfer_file, const struct cred *from, + const struct cred *to, struct file *file) LSM_HOOK(int, 0, ptrace_access_check, struct task_struct *child, unsigned int mode) LSM_HOOK(int, 0, ptrace_traceme, struct task_struct *parent) diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 5c4c5c0602cb..59024618554e 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -1313,22 +1313,22 @@ * * @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 diff --git a/include/linux/security.h b/include/linux/security.h index 5b7288521300..6344d3362df7 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -258,13 +258,13 @@ 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, @@ -508,25 +508,25 @@ 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 9ffa9e9c5c55..67264cb08fb3 100644 --- a/security/security.c +++ b/security/security.c @@ -747,25 +747,25 @@ static int lsm_superblock_alloc(struct super_block *sb) /* 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 e7ebd45ca345..c8bf3db90c8b 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -255,29 +255,6 @@ static inline u32 task_sid_obj(const struct task_struct *task) return sid; } -/* - * get the security ID of a task for use with binder - */ -static inline u32 task_sid_binder(const struct task_struct *task) -{ - /* - * In many case where this function is used we should be using the - * task's subjective SID, but we can't reliably access the subjective - * creds of a task other than our own so we must use the objective - * creds/SID, which are safe to access. The downside is that if a task - * is temporarily overriding it's creds it will not be reflected here; - * however, it isn't clear that binder would handle that case well - * anyway. - * - * If this ever changes and we can safely reference the subjective - * creds/SID of another task, this function will make it easier to - * identify the various places where we make use of the task SIDs in - * the binder code. It is also likely that we will need to adjust - * the main drivers/android binder code as well. - */ - return task_sid_obj(task); -} - static int inode_doinit_with_dentry(struct inode *inode, struct dentry *opt_dentry); /* @@ -2066,18 +2043,19 @@ 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) { return avc_has_perm(&selinux_state, - current_sid(), task_sid_binder(mgr), 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_binder(from); + u32 fromsid = cred_sid(from); + u32 tosid = cred_sid(to); int rc; if (mysid != fromsid) { @@ -2088,24 +2066,24 @@ static int selinux_binder_transaction(struct task_struct *from, return rc; } - return avc_has_perm(&selinux_state, fromsid, task_sid_binder(to), + 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) { return avc_has_perm(&selinux_state, - task_sid_binder(from), task_sid_binder(to), + 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_binder(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; From patchwork Tue Oct 12 16:56:14 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Todd Kjos X-Patchwork-Id: 12553247 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 08BC1C4332F for ; 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Tue, 12 Oct 2021 09:56:30 -0700 (PDT) Date: Tue, 12 Oct 2021 09:56:14 -0700 In-Reply-To: <20211012165614.2873369-1-tkjos@google.com> Message-Id: <20211012165614.2873369-4-tkjos@google.com> Mime-Version: 1.0 References: <20211012165614.2873369-1-tkjos@google.com> X-Mailer: git-send-email 2.33.0.882.g93a45727a2-goog Subject: [PATCH v5 3/3] binder: use cred instead of task for getsecid From: Todd Kjos To: 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, linux-kernel@vger.kernel.org Cc: joel@joelfernandes.org, kernel-team@android.com, Todd Kjos , kernel test robot , stable@vger.kernel.org Precedence: bulk List-ID: Use the 'struct cred' saved at binder_open() to lookup the security ID via security_cred_getsecid(). This ensures that the security context that opened binder is the one used to generate the secctx. Fixes: ec74136ded79 ("binder: create node flag to request sender's security context") Signed-off-by: Todd Kjos Suggested-by: Stephen Smalley Reported-by: kernel test robot Cc: stable@vger.kernel.org # 5.4+ --- v3: added this patch to series v4: fix build-break for !CONFIG_SECURITY v5: set *secid=0 for !CONFIG_SECURITY version of secuirty_cred_getsecid() drivers/android/binder.c | 11 +---------- include/linux/security.h | 5 +++++ 2 files changed, 6 insertions(+), 10 deletions(-) diff --git a/drivers/android/binder.c b/drivers/android/binder.c index bc15325f0579..26382e982c5e 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -2722,16 +2722,7 @@ static void binder_transaction(struct binder_proc *proc, u32 secid; size_t added_size; - /* - * Arguably this should be the task's subjective LSM secid but - * we can't reliably access the subjective creds of a task - * other than our own so we must use the objective creds, which - * are safe to access. The downside is that if a task is - * temporarily overriding it's creds it will not be reflected - * here; however, it isn't clear that binder would handle that - * case well anyway. - */ - security_task_getsecid_obj(proc->tsk, &secid); + security_cred_getsecid(proc->cred, &secid); ret = security_secid_to_secctx(secid, &secctx, &secctx_sz); if (ret) { return_error = BR_FAILED_REPLY; diff --git a/include/linux/security.h b/include/linux/security.h index 6344d3362df7..46a02ce34d00 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -1041,6 +1041,11 @@ static inline void security_transfer_creds(struct cred *new, { } +static inline void security_cred_getsecid(const struct cred *c, u32 *secid) +{ + *secid = 0; +} + static inline int security_kernel_act_as(struct cred *cred, u32 secid) { return 0;