From patchwork Tue Aug 18 15:42:15 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Krzysztof Struczynski X-Patchwork-Id: 11721899 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B0A8B722 for ; Tue, 18 Aug 2020 16:00:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 99FDE20639 for ; Tue, 18 Aug 2020 16:00:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726640AbgHRQAQ (ORCPT ); Tue, 18 Aug 2020 12:00:16 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2638 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726990AbgHRPpg (ORCPT ); Tue, 18 Aug 2020 11:45:36 -0400 Received: from lhreml722-chm.china.huawei.com (unknown [172.18.7.106]) by Forcepoint Email with ESMTP id 545BE99586F4F7D8E732; Tue, 18 Aug 2020 16:45:35 +0100 (IST) Received: from kstruczy-linux-box (10.204.65.138) by lhreml722-chm.china.huawei.com (10.201.108.73) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1913.5; Tue, 18 Aug 2020 16:45:33 +0100 Received: by kstruczy-linux-box (sSMTP sendmail emulation); Tue, 18 Aug 2020 17:45:36 +0200 From: To: , , , CC: , , , , , , , , , , Krzysztof Struczynski Subject: [RFC PATCH 15/30] ima: Add a reader counter to the integrity inode data Date: Tue, 18 Aug 2020 17:42:15 +0200 Message-ID: <20200818154230.14016-6-krzysztof.struczynski@huawei.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200818154230.14016-1-krzysztof.struczynski@huawei.com> References: <20200818154230.14016-1-krzysztof.struczynski@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.204.65.138] X-ClientProxiedBy: fraeml707-chm.china.huawei.com (10.206.15.35) To lhreml722-chm.china.huawei.com (10.201.108.73) X-CFilter-Loop: Reflected Sender: linux-integrity-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org From: Krzysztof Struczynski To detect ToMToU violations reader counter of the given inode is checked. This is not enough, because the reader may exist in a different ima namespace. Per inode reader counter tracks readers in all ima namespaces, whereas the per namespace counter is necessary to avoid false positives. Add a new reader counter to the integrity inode cache entry. Signed-off-by: Krzysztof Struczynski --- security/integrity/ima/ima_main.c | 71 ++++++++++++++++++++++--------- security/integrity/integrity.h | 18 ++++++++ 2 files changed, 70 insertions(+), 19 deletions(-) diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index b933c7e6c8e1..6555cdf6b65e 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -28,6 +28,11 @@ #include "ima.h" +struct ima_file_data { + struct ima_namespace *ima_ns; + bool is_readcount; +}; + int ima_hash_algo = HASH_ALGO_SHA1; static int hash_setup_done; @@ -116,8 +121,8 @@ static void ima_rdwr_violation_check(struct file *file, iint = integrity_iint_rb_find(ima_ns->iint_tree, inode); /* IMA_MEASURE is set from reader side */ - if (iint && test_bit(IMA_MUST_MEASURE, - &iint->atomic_flags)) + if (iint && atomic_read(&iint->readcount) && + test_bit(IMA_MUST_MEASURE, &iint->atomic_flags)) send_tomtou = true; } } else { @@ -171,7 +176,7 @@ static void ima_check_last_writer(struct integrity_iint_cache *iint, { fmode_t mode = file->f_mode; bool update; - struct ima_namespace *ima_ns = (struct ima_namespace *)file->f_ima; + struct ima_file_data *f_data = (struct ima_file_data *)file->f_ima; if (!(mode & FMODE_WRITE)) return; @@ -186,7 +191,7 @@ static void ima_check_last_writer(struct integrity_iint_cache *iint, iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE); iint->measured_pcrs = 0; - ima_check_active_ns(ima_ns, inode); + ima_check_active_ns(f_data->ima_ns, inode); if (update) ima_update_xattr(iint, file); @@ -207,8 +212,18 @@ static void ima_check_last_writer(struct integrity_iint_cache *iint, */ int ima_file_alloc(struct file *file) { - file->f_ima = get_current_ns(); - get_ima_ns((struct ima_namespace *)file->f_ima); + struct ima_file_data *f_data; + + f_data = kmalloc(sizeof(struct ima_file_data), GFP_KERNEL); + if (!f_data) + return -ENOMEM; + + f_data->ima_ns = get_current_ns(); + f_data->is_readcount = false; + get_ima_ns(f_data->ima_ns); + + file->f_ima = f_data; + return 0; } @@ -222,27 +237,33 @@ void ima_file_free(struct file *file) { struct inode *inode = file_inode(file); struct integrity_iint_cache *iint; - struct ima_namespace *ima_ns = (struct ima_namespace *)file->f_ima; + struct ima_file_data *f_data = (struct ima_file_data *)file->f_ima; if (unlikely(!(file->f_mode & FMODE_OPENED))) goto out; - if (!ima_ns->policy_data->ima_policy_flag || !S_ISREG(inode->i_mode)) + if (!f_data->ima_ns->policy_data->ima_policy_flag || + !S_ISREG(inode->i_mode)) goto out; - iint = integrity_iint_rb_find(ima_ns->iint_tree, inode); + iint = integrity_iint_rb_find(f_data->ima_ns->iint_tree, inode); if (!iint) goto out; ima_check_last_writer(iint, inode, file); + + if (f_data->is_readcount) + iint_readcount_dec(iint); out: - put_ima_ns(ima_ns); + put_ima_ns(f_data->ima_ns); + kfree(f_data); } static int process_ns_measurement(struct file *file, const struct cred *cred, u32 secid, char *buf, loff_t size, int mask, enum ima_hooks func, - struct ima_namespace *ima_ns) + struct ima_namespace *ima_ns, + bool readcount_open) { struct inode *inode = file_inode(file); struct integrity_iint_cache *iint = NULL; @@ -262,6 +283,12 @@ static int process_ns_measurement(struct file *file, const struct cred *cred, if (!ima_ns->policy_data->ima_policy_flag) return 0; + if (ima_ns != current_ima_ns) { + iint = integrity_iint_rb_find(ima_ns->iint_tree, inode); + if (!iint) + return 0; + } + /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action * bitmask based on the appraise/audit/measurement policy. * Included is the appraise submask. @@ -282,12 +309,18 @@ static int process_ns_measurement(struct file *file, const struct cred *cred, inode_lock(inode); - if (action) { + if (action && !iint) { iint = integrity_inode_rb_get(ima_ns->iint_tree, inode); if (!iint) rc = -ENOMEM; } + if ((ima_ns == current_ima_ns) && iint && readcount_open && + ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)) { + iint_readcount_inc(iint); + ((struct ima_file_data *)file->f_ima)->is_readcount = true; + } + if (!rc && violation_check) ima_rdwr_violation_check(file, iint, action & IMA_MEASURE, &pathbuf, &pathname, filename, ima_ns); @@ -429,7 +462,7 @@ static int process_ns_measurement(struct file *file, const struct cred *cred, static int process_measurement(struct file *file, const struct cred *cred, u32 secid, char *buf, loff_t size, int mask, - enum ima_hooks func) + enum ima_hooks func, bool readcount_open) { int ret; struct ima_namespace *ima_ns; @@ -444,7 +477,7 @@ static int process_measurement(struct file *file, const struct cred *cred, continue; ret = process_ns_measurement(file, cred, secid, buf, size, mask, - func, ima_ns); + func, ima_ns, readcount_open); if (ret != 0) break; } @@ -471,7 +504,7 @@ int ima_file_mmap(struct file *file, unsigned long prot) if (file && (prot & PROT_EXEC)) { security_task_getsecid(current, &secid); return process_measurement(file, current_cred(), secid, NULL, - 0, MAY_EXEC, MMAP_CHECK); + 0, MAY_EXEC, MMAP_CHECK, true); } return 0; @@ -551,13 +584,13 @@ int ima_bprm_check(struct linux_binprm *bprm) security_task_getsecid(current, &secid); ret = process_measurement(bprm->file, current_cred(), secid, NULL, 0, - MAY_EXEC, BPRM_CHECK); + MAY_EXEC, BPRM_CHECK, false); if (ret) return ret; security_cred_getsecid(bprm->cred, &secid); return process_measurement(bprm->file, bprm->cred, secid, NULL, 0, - MAY_EXEC, CREDS_CHECK); + MAY_EXEC, CREDS_CHECK, false); } /** @@ -577,7 +610,7 @@ int ima_file_check(struct file *file, int mask) security_task_getsecid(current, &secid); return process_measurement(file, current_cred(), secid, NULL, 0, mask & (MAY_READ | MAY_WRITE | MAY_EXEC | - MAY_APPEND), FILE_CHECK); + MAY_APPEND), FILE_CHECK, true); } EXPORT_SYMBOL_GPL(ima_file_check); @@ -779,7 +812,7 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size, func = read_idmap[read_id] ?: FILE_CHECK; security_task_getsecid(current, &secid); return process_measurement(file, current_cred(), secid, buf, size, - MAY_READ, func); + MAY_READ, func, false); } /** diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h index 721d1850e4f9..c2981a98547e 100644 --- a/security/integrity/integrity.h +++ b/security/integrity/integrity.h @@ -17,6 +17,7 @@ #include #include #include +#include /* iint action cache flags */ #define IMA_MEASURE 0x00000001 @@ -138,6 +139,9 @@ struct integrity_iint_cache { enum integrity_status ima_creds_status:4; enum integrity_status evm_status:4; struct ima_digest_data *ima_hash; + atomic_t readcount; /* Reader counter, incremented only in FILE_CHECK or + * MMAP_CHECK hooks, used for ima violation check. + */ }; struct integrity_iint_tree { @@ -294,3 +298,17 @@ static inline void __init add_to_platform_keyring(const char *source, { } #endif + +#ifdef CONFIG_IMA +static inline void iint_readcount_inc(struct integrity_iint_cache *iint) +{ + atomic_inc(&iint->readcount); +} +static inline void iint_readcount_dec(struct integrity_iint_cache *iint) +{ + if (WARN_ON(!atomic_read(&iint->readcount))) + return; + + atomic_dec(&iint->readcount); +} +#endif