From patchwork Thu Mar 18 21:53:02 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ondrej Mosnacek X-Patchwork-Id: 12149279 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 905DCC433DB for ; Thu, 18 Mar 2021 21:54:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6DD5264F38 for ; Thu, 18 Mar 2021 21:54:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231137AbhCRVxl (ORCPT ); Thu, 18 Mar 2021 17:53:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:53301 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231770AbhCRVx1 (ORCPT ); Thu, 18 Mar 2021 17:53:27 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616104406; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Xuml6FX+QV3znNsmhXkEQUKuBbFZHIk7R0h/7PdbebI=; b=Mc2Yx6sipWXHw66IcGbCqwBE7THF6L7mcOUoAnu7LYMCnvk5+leOdqQUDwXQcMHQ9450RA djP4zdDYuuhfJlhfaYVLEmO1ckprtzSWI261wE9o4IEBlS4DrIbUvrNIbS75icvozf9bZ1 ywaywMwsPHhT9c0nlHCjsFbGj5WzikA= Received: from mail-ej1-f72.google.com (mail-ej1-f72.google.com [209.85.218.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-37-H5KPB4R9Mrm-KsC1tzWgug-1; Thu, 18 Mar 2021 17:53:10 -0400 X-MC-Unique: H5KPB4R9Mrm-KsC1tzWgug-1 Received: by mail-ej1-f72.google.com with SMTP id au15so17385315ejc.8 for ; Thu, 18 Mar 2021 14:53:10 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Xuml6FX+QV3znNsmhXkEQUKuBbFZHIk7R0h/7PdbebI=; b=ZczkLzhBGjeq0RW4nmWvP2p3jwUB1OVC5cgRdyA20Ilk149ayE92puE/tf3A6zg7OI 0CalVKoF7tXjojsBRAZS2STVj/MlJkznZSTJoPKR034LlqF80tdAB28/7wupg/OkLuJx Z6nE8HCA6oq24Unt6BiGacaZEI0Tbo6IJvv6/mKR7bgworL80sy19A1dXfsMvNuWL9B2 SpLMUyU0jIQq4GbXdWpgvKWbrV4Cxpa4Xc1bbfxb8ob/WBVb2CAVYmmIzX9s2mHXt2/b b3c+WvukemznZyD9h0w9yxFkyEFF/74abbfpnkRmfo5iege/lbupx4GmO1RDNl8Vw59Y By4g== X-Gm-Message-State: AOAM530b5c4GVur3LpLqg3a3h6RUP9aRqOR3Ody2iaMYDK+69/Qobyey WBl5+ZwnN9LzkFkbrrxla5x9sJiaO+8df8F9mk0E7P/owkse/BfSax4Ug83DTCrOkwslatBVw8P xVEgncGYr8q/KWK9xgQUbjp7N4c9FzuN/8PT8/7HaEOCt3PVyZ6uCkODnkB9/KhsZm0R1ZQ== X-Received: by 2002:a17:907:9862:: with SMTP id ko2mr728200ejc.222.1616104388717; Thu, 18 Mar 2021 14:53:08 -0700 (PDT) X-Google-Smtp-Source: ABdhPJw4eqtdcZ7XbmuiyKvhLIb7WVbJgRqeaWisFCJWTZ3eaOe1XGxfBkTdm5BIuWs13xhiaUMhdA== X-Received: by 2002:a17:907:9862:: with SMTP id ko2mr728185ejc.222.1616104388514; Thu, 18 Mar 2021 14:53:08 -0700 (PDT) Received: from omos.redhat.com ([2a02:8308:b105:dd00:277b:6436:24db:9466]) by smtp.gmail.com with ESMTPSA id a17sm2620255ejf.20.2021.03.18.14.53.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Mar 2021 14:53:08 -0700 (PDT) From: Ondrej Mosnacek To: selinux@vger.kernel.org, Paul Moore Cc: Stephen Smalley , Tyler Hicks Subject: [PATCH v3 2/3] selinux: fix variable scope issue in live sidtab conversion Date: Thu, 18 Mar 2021 22:53:02 +0100 Message-Id: <20210318215303.2578052-3-omosnace@redhat.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210318215303.2578052-1-omosnace@redhat.com> References: <20210318215303.2578052-1-omosnace@redhat.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org Commit 02a52c5c8c3b ("selinux: move policy commit after updating selinuxfs") moved the selinux_policy_commit() call out of security_load_policy() into sel_write_load(), which caused a subtle yet rather serious bug. The problem is that security_load_policy() passes a reference to the convert_params local variable to sidtab_convert(), which stores it in the sidtab, where it may be accessed until the policy is swapped over and RCU synchronized. Before 02a52c5c8c3b, selinux_policy_commit() was called directly from security_load_policy(), so the convert_params pointer remained valid all the way until the old sidtab was destroyed, but now that's no longer the case and calls to sidtab_context_to_sid() on the old sidtab after security_load_policy() returns may cause invalid memory accesses. This can be easily triggered using the stress test from commit ee1a84fdfeed ("selinux: overhaul sidtab to fix bug and improve performance"): ``` function rand_cat() { echo $(( $RANDOM % 1024 )) } function do_work() { while true; do echo -n "system_u:system_r:kernel_t:s0:c$(rand_cat),c$(rand_cat)" \ >/sys/fs/selinux/context 2>/dev/null || true done } do_work >/dev/null & do_work >/dev/null & do_work >/dev/null & while load_policy; do echo -n .; sleep 0.1; done kill %1 kill %2 kill %3 ``` Fix this by allocating the temporary sidtab convert structures dynamically and passing them among the selinux_policy_{load,cancel,commit} functions. Fixes: 02a52c5c8c3b ("selinux: move policy commit after updating selinuxfs") Tested-by: Tyler Hicks Reviewed-by: Tyler Hicks Signed-off-by: Ondrej Mosnacek --- security/selinux/include/security.h | 15 +++++-- security/selinux/selinuxfs.c | 10 ++--- security/selinux/ss/services.c | 63 ++++++++++++++++++----------- 3 files changed, 55 insertions(+), 33 deletions(-) diff --git a/security/selinux/include/security.h b/security/selinux/include/security.h index 7130c9648ad1..ac0ece01305a 100644 --- a/security/selinux/include/security.h +++ b/security/selinux/include/security.h @@ -219,14 +219,21 @@ static inline bool selinux_policycap_genfs_seclabel_symlinks(void) return READ_ONCE(state->policycap[POLICYDB_CAPABILITY_GENFS_SECLABEL_SYMLINKS]); } +struct selinux_policy_convert_data; + +struct selinux_load_state { + struct selinux_policy *policy; + struct selinux_policy_convert_data *convert_data; +}; + int security_mls_enabled(struct selinux_state *state); int security_load_policy(struct selinux_state *state, - void *data, size_t len, - struct selinux_policy **newpolicyp); + void *data, size_t len, + struct selinux_load_state *load_state); void selinux_policy_commit(struct selinux_state *state, - struct selinux_policy *newpolicy); + struct selinux_load_state *load_state); void selinux_policy_cancel(struct selinux_state *state, - struct selinux_policy *policy); + struct selinux_load_state *load_state); int security_read_policy(struct selinux_state *state, void **data, size_t *len); int security_read_state_kernel(struct selinux_state *state, diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c index 37b32b0035f6..dc7297abe4ea 100644 --- a/security/selinux/selinuxfs.c +++ b/security/selinux/selinuxfs.c @@ -619,7 +619,7 @@ static ssize_t sel_write_load(struct file *file, const char __user *buf, { struct selinux_fs_info *fsi = file_inode(file)->i_sb->s_fs_info; - struct selinux_policy *newpolicy; + struct selinux_load_state load_state; ssize_t length; void *data = NULL; @@ -645,19 +645,19 @@ static ssize_t sel_write_load(struct file *file, const char __user *buf, if (copy_from_user(data, buf, count) != 0) goto out; - length = security_load_policy(fsi->state, data, count, &newpolicy); + length = security_load_policy(fsi->state, data, count, &load_state); if (length) { pr_warn_ratelimited("SELinux: failed to load policy\n"); goto out; } - length = sel_make_policy_nodes(fsi, newpolicy); + length = sel_make_policy_nodes(fsi, load_state.policy); if (length) { - selinux_policy_cancel(fsi->state, newpolicy); + selinux_policy_cancel(fsi->state, &load_state); goto out; } - selinux_policy_commit(fsi->state, newpolicy); + selinux_policy_commit(fsi->state, &load_state); length = count; diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c index f37375c9553f..08ac1d01c743 100644 --- a/security/selinux/ss/services.c +++ b/security/selinux/ss/services.c @@ -67,6 +67,17 @@ #include "policycap_names.h" #include "ima.h" +struct convert_context_args { + struct selinux_state *state; + struct policydb *oldp; + struct policydb *newp; +}; + +struct selinux_policy_convert_data { + struct convert_context_args args; + struct sidtab_convert_params sidtab_params; +}; + /* Forward declaration. */ static int context_struct_to_string(struct policydb *policydb, struct context *context, @@ -1974,12 +1985,6 @@ static inline int convert_context_handle_invalid_context( return 0; } -struct convert_context_args { - struct selinux_state *state; - struct policydb *oldp; - struct policydb *newp; -}; - /* * Convert the values in the security context * structure `oldc' from the values specified @@ -2159,7 +2164,7 @@ static void selinux_policy_cond_free(struct selinux_policy *policy) } void selinux_policy_cancel(struct selinux_state *state, - struct selinux_policy *policy) + struct selinux_load_state *load_state) { struct selinux_policy *oldpolicy; @@ -2167,7 +2172,8 @@ void selinux_policy_cancel(struct selinux_state *state, lockdep_is_held(&state->policy_mutex)); sidtab_cancel_convert(oldpolicy->sidtab); - selinux_policy_free(policy); + selinux_policy_free(load_state->policy); + kfree(load_state->convert_data); } static void selinux_notify_policy_change(struct selinux_state *state, @@ -2183,9 +2189,9 @@ static void selinux_notify_policy_change(struct selinux_state *state, } void selinux_policy_commit(struct selinux_state *state, - struct selinux_policy *newpolicy) + struct selinux_load_state *load_state) { - struct selinux_policy *oldpolicy; + struct selinux_policy *oldpolicy, *newpolicy = load_state->policy; u32 seqno; oldpolicy = rcu_dereference_protected(state->policy, @@ -2225,6 +2231,7 @@ void selinux_policy_commit(struct selinux_state *state, /* Free the old policy */ synchronize_rcu(); selinux_policy_free(oldpolicy); + kfree(load_state->convert_data); /* Notify others of the policy change */ selinux_notify_policy_change(state, seqno); @@ -2241,11 +2248,10 @@ void selinux_policy_commit(struct selinux_state *state, * loading the new policy. */ int security_load_policy(struct selinux_state *state, void *data, size_t len, - struct selinux_policy **newpolicyp) + struct selinux_load_state *load_state) { struct selinux_policy *newpolicy, *oldpolicy; - struct sidtab_convert_params convert_params; - struct convert_context_args args; + struct selinux_policy_convert_data *convert_data; int rc = 0; struct policy_file file = { data, len }, *fp = &file; @@ -2275,10 +2281,10 @@ int security_load_policy(struct selinux_state *state, void *data, size_t len, goto err_mapping; } - if (!selinux_initialized(state)) { /* First policy load, so no need to preserve state from old policy */ - *newpolicyp = newpolicy; + load_state->policy = newpolicy; + load_state->convert_data = NULL; return 0; } @@ -2292,29 +2298,38 @@ int security_load_policy(struct selinux_state *state, void *data, size_t len, goto err_free_isids; } + convert_data = kmalloc(sizeof(*convert_data), GFP_KERNEL); + if (!convert_data) { + rc = -ENOMEM; + goto err_free_isids; + } + /* * Convert the internal representations of contexts * in the new SID table. */ - args.state = state; - args.oldp = &oldpolicy->policydb; - args.newp = &newpolicy->policydb; + convert_data->args.state = state; + convert_data->args.oldp = &oldpolicy->policydb; + convert_data->args.newp = &newpolicy->policydb; - convert_params.func = convert_context; - convert_params.args = &args; - convert_params.target = newpolicy->sidtab; + convert_data->sidtab_params.func = convert_context; + convert_data->sidtab_params.args = &convert_data->args; + convert_data->sidtab_params.target = newpolicy->sidtab; - rc = sidtab_convert(oldpolicy->sidtab, &convert_params); + rc = sidtab_convert(oldpolicy->sidtab, &convert_data->sidtab_params); if (rc) { pr_err("SELinux: unable to convert the internal" " representation of contexts in the new SID" " table\n"); - goto err_free_isids; + goto err_free_convert_data; } - *newpolicyp = newpolicy; + load_state->policy = newpolicy; + load_state->convert_data = convert_data; return 0; +err_free_convert_data: + kfree(convert_data); err_free_isids: sidtab_destroy(newpolicy->sidtab); err_mapping: