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Fri, 28 Feb 2025 20:55:24 +0000 Received: from smtpav05.fra02v.mail.ibm.com (smtpav05.fra02v.mail.ibm.com [10.20.54.104]) by smtprelay04.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 51SKtKeO30802666 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 28 Feb 2025 20:55:20 GMT Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 63DCD20043; Fri, 28 Feb 2025 20:55:20 +0000 (GMT) Received: from smtpav05.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id BBE0920040; Fri, 28 Feb 2025 20:55:18 +0000 (GMT) Received: from li-43857255-d5e6-4659-90f1-fc5cee4750ad.ibm.com.com (unknown [9.61.94.47]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 28 Feb 2025 20:55:18 +0000 (GMT) From: Mimi Zohar To: linux-integrity@vger.kernel.org Cc: Mimi Zohar , roberto.sassu@huawei.com, Stefan Berger , Petr Vorel Subject: [PATCH v2 2/2] ima: limit the number of ToMToU integrity violations Date: Fri, 28 Feb 2025 15:55:05 -0500 Message-ID: <20250228205505.476845-3-zohar@linux.ibm.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250228205505.476845-1-zohar@linux.ibm.com> References: <20250228205505.476845-1-zohar@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: _FzJdi_XbgNJhNmBsAgvaf_uEsYw6dyW X-Proofpoint-GUID: _FzJdi_XbgNJhNmBsAgvaf_uEsYw6dyW X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-28_06,2025-02-28_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 clxscore=1015 adultscore=0 mlxlogscore=999 spamscore=0 phishscore=0 malwarescore=0 lowpriorityscore=0 impostorscore=0 priorityscore=1501 suspectscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2502100000 definitions=main-2502280148 Each time a file in policy, that is already opened for read, is opened for write, a Time-of-Measure-Time-of-Use (ToMToU) integrity violation audit message is emitted and a violation record is added to the IMA measurement list. This occurs even if a ToMToU violation has already been recorded. Limit the number of ToMToU integrity violations per file open for read. Note: The IMA_MAY_EMIT_TOMTOU atomic flag must be set from the reader side based on policy. This may result in a per file open for read ToMToU violation. Since IMA_MUST_MEASURE is only used for violations, rename the atomic IMA_MUST_MEASURE flag to IMA_MAY_EMIT_TOMTOU. Tested-by: Stefan Berger Reviewed-by: Petr Vorel Tested-by: Petr Vorel Signed-off-by: Mimi Zohar --- Changelog v2: - Based on Roberto's review, renamed the atomic flag name, updated the patch description. - Added Petr's and Stefan's tags. security/integrity/ima/ima.h | 2 +- security/integrity/ima/ima_main.c | 7 ++++--- 2 files changed, 5 insertions(+), 4 deletions(-) -- 2.48.1 diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index 3423b3088de5..e0489c6f7f59 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -181,7 +181,7 @@ struct ima_kexec_hdr { #define IMA_UPDATE_XATTR 1 #define IMA_CHANGE_ATTR 2 #define IMA_DIGSIG 3 -#define IMA_MUST_MEASURE 4 +#define IMA_MAY_EMIT_TOMTOU 4 #define IMA_EMITTED_OPENWRITERS 5 /* IMA integrity metadata associated with an inode */ diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 95118c1887cb..f3e7ac513db3 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -129,14 +129,15 @@ static void ima_rdwr_violation_check(struct file *file, if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) { if (!iint) iint = ima_iint_find(inode); + /* IMA_MEASURE is set from reader side */ - if (iint && test_bit(IMA_MUST_MEASURE, - &iint->atomic_flags)) + if (iint && test_and_clear_bit(IMA_MAY_EMIT_TOMTOU, + &iint->atomic_flags)) send_tomtou = true; } } else { if (must_measure) - set_bit(IMA_MUST_MEASURE, &iint->atomic_flags); + set_bit(IMA_MAY_EMIT_TOMTOU, &iint->atomic_flags); /* Limit number of open_writers violations */ if (inode_is_open_for_write(inode) && must_measure) {