From patchwork Mon Mar 29 07:56:35 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 411465 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 1A60CC433E2 for ; Mon, 29 Mar 2021 08:21:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB19F619BC for ; Mon, 29 Mar 2021 08:21:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233112AbhC2IVE (ORCPT ); Mon, 29 Mar 2021 04:21:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:36014 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232256AbhC2IUL (ORCPT ); Mon, 29 Mar 2021 04:20:11 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 13556619CA; Mon, 29 Mar 2021 08:19:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1617006000; bh=ZMl16UAd9pVTrK0QjJ1Fi3BOD/lFDmcZlzwI6WsV3y0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AoK1ri9tuVkfQnqM+SaA+s9pNDaa21djjSio3sN1vbLP43NSJgzGND9oCbJ5Cu/TE 6F3yLRRYGaovbWP4r1hthqXOXYxd4af/Op8r4bOxverrx9xspbrS6c1qKcGZkLsGPR QisicGlEZRCNcbYq4dUClglA3kY/Ol5fbwggeoOM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tyler Hicks , Ondrej Mosnacek , Paul Moore Subject: [PATCH 5.10 064/221] selinux: fix variable scope issue in live sidtab conversion Date: Mon, 29 Mar 2021 09:56:35 +0200 Message-Id: <20210329075631.325895612@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210329075629.172032742@linuxfoundation.org> References: <20210329075629.172032742@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Ondrej Mosnacek commit 6406887a12ee5dcdaffff1a8508d91113d545559 upstream. 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") Cc: stable@vger.kernel.org Tested-by: Tyler Hicks Reviewed-by: Tyler Hicks Signed-off-by: Ondrej Mosnacek [PM: merge fuzz in security.h and services.c] Signed-off-by: Paul Moore Signed-off-by: Greg Kroah-Hartman --- security/selinux/include/security.h | 15 ++++++-- security/selinux/selinuxfs.c | 10 ++--- security/selinux/ss/services.c | 65 ++++++++++++++++++++++-------------- 3 files changed, 56 insertions(+), 34 deletions(-) --- a/security/selinux/include/security.h +++ b/security/selinux/include/security.h @@ -219,14 +219,21 @@ static inline bool selinux_policycap_gen 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); --- a/security/selinux/selinuxfs.c +++ b/security/selinux/selinuxfs.c @@ -616,7 +616,7 @@ static ssize_t sel_write_load(struct fil { 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; @@ -642,19 +642,19 @@ static ssize_t sel_write_load(struct fil 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; --- a/security/selinux/ss/services.c +++ b/security/selinux/ss/services.c @@ -66,6 +66,17 @@ #include "audit.h" #include "policycap_names.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, @@ -1975,12 +1986,6 @@ static inline int convert_context_handle 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 @@ -2160,7 +2165,7 @@ static void selinux_policy_cond_free(str } void selinux_policy_cancel(struct selinux_state *state, - struct selinux_policy *policy) + struct selinux_load_state *load_state) { struct selinux_policy *oldpolicy; @@ -2168,7 +2173,8 @@ void selinux_policy_cancel(struct selinu 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 } 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 selinu /* 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 selinu * 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_ 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_ 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_params.func = convert_context; - convert_params.args = &args; - convert_params.target = newpolicy->sidtab; + convert_data->args.state = state; + convert_data->args.oldp = &oldpolicy->policydb; + convert_data->args.newp = &newpolicy->policydb; + + 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: