From nobody Thu Apr 2 20:27:05 2026 Received: from frasgout13.his.huawei.com (frasgout13.his.huawei.com [14.137.139.46]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 108CD4279E0; Thu, 26 Mar 2026 17:31:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=14.137.139.46 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774546302; cv=none; b=rwUJcANyb3Ozym8zUfi+yIWvzclK6rbaJ4WipHvI76YsVa8muveksQY3OR4m/7eBS12OJaLh7cY3j3/ttq4QgpLA+4U7sxngNlEpE5dCEFdgTwusA2IYDP3dbrXOuOyudTj6gZxWK6NpfeiSxye9FpQ9bAkgXOCnJHZTeaqQ87s= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774546302; c=relaxed/simple; bh=EOZOjyjMg6/Fn5W/fcIBelXq1e2DV8pmyX8Hk++1dSw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ez6q+D6smHXCF1lZSkXsaDoKN72uabTftxVMB0ZQn75aC0qDqgemin5IJSxVjhWT8Vs5uFxtop68V86W64BIddMAIzTGJqcEMzFCKhlNXN4H8yvtfEbzdVU/vuvSjKtMRZJaQwmTdXQhgcOvVU1YiIL/ZPB75dRuzMqBVd8DKU4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com; spf=pass smtp.mailfrom=huaweicloud.com; arc=none smtp.client-ip=14.137.139.46 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=huaweicloud.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huaweicloud.com Received: from mail.maildlp.com (unknown [172.18.224.235]) by frasgout13.his.huawei.com (SkyGuard) with ESMTPS id 4fhW1r0TMkzpVh5; Fri, 27 Mar 2026 01:27:44 +0800 (CST) Received: from mail02.huawei.com (unknown [7.182.16.47]) by mail.maildlp.com (Postfix) with ESMTP id 4DCE840560; Fri, 27 Mar 2026 01:31:32 +0800 (CST) Received: from huaweicloud.com (unknown [10.204.63.22]) by APP1 (Coremail) with SMTP id LxC2BwB3Yu84bcVppGUvAQ--.1881S8; Thu, 26 Mar 2026 18:31:31 +0100 (CET) From: Roberto Sassu To: corbet@lwn.net, skhan@linuxfoundation.org, zohar@linux.ibm.com, dmitry.kasatkin@gmail.com, eric.snowberg@oracle.com, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, gregorylumen@linux.microsoft.com, chenste@linux.microsoft.com, nramas@linux.microsoft.com, Roberto Sassu Subject: [PATCH v4 06/13] ima: Mediate open/release method of the measurements list Date: Thu, 26 Mar 2026 18:30:04 +0100 Message-ID: <20260326173011.1191815-7-roberto.sassu@huaweicloud.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260326173011.1191815-1-roberto.sassu@huaweicloud.com> References: <20260326173011.1191815-1-roberto.sassu@huaweicloud.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: LxC2BwB3Yu84bcVppGUvAQ--.1881S8 X-Coremail-Antispam: 1UD129KBjvJXoWxur1kCFW7ZFy5CFyDJryUAwb_yoWrCr43pa 93C3yrCr1kJrWfWFn7Ga47Zr4F9a4rKa15Wr4DJa4fAF1rJr9F9F4Yyr12kFs8tryrGr18 Xw4qqr45uas0yaDanT9S1TB71UUUUUDqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUPlb4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUAV Cq3wA2048vs2IY020Ec7CjxVAFwI0_Xr0E3s1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0 rcxSw2x7M28EF7xvwVC0I7IYx2IY67AKxVW5JVW7JwA2z4x0Y4vE2Ix0cI8IcVCY1x0267 AKxVW8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_Gr0_Cr1l84ACjcxK6I8E87Iv6xkF7I0E 14v26r4UJVWxJr1le2I262IYc4CY6c8Ij28IcVAaY2xG8wAqx4xG64xvF2IEw4CE5I8CrV C2j2WlYx0E2Ix0cI8IcVAFwI0_Jrv_JF1lYx0Ex4A2jsIE14v26r1j6r4UMcvjeVCFs4IE 7xkEbVWUJVW8JwACjcxG0xvY0x0EwIxGrwACI402YVCY1x02628vn2kIc2xKxwCY1x0262 kKe7AKxVWrXVW3AwCF04k20xvY0x0EwIxGrwCFx2IqxVCFs4IE7xkEbVWUJVW8JwC20s02 6c02F40E14v26r1j6r18MI8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_GF v_WrylIxkGc2Ij64vIr41lIxAIcVC0I7IYx2IY67AKxVW5JVW7JwCI42IY6xIIjxv20xvE c7CjxVAFwI0_Gr1j6F4UJwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aV AFwI0_Gr0_Cr1lIxAIcVC2z280aVCY1x0267AKxVW8Jr0_Cr1UYxBIdaVFxhVjvjDU0xZF pf9x07jhXo7UUUUU= X-CM-SenderInfo: purev21wro2thvvxqx5xdzvxpfor3voofrz/1tbiAQAEBGnEnSsT2wAAsS Content-Type: text/plain; charset="utf-8" From: Roberto Sassu Introduce the ima_measure_users counter, to implement a semaphore-like locking scheme where the binary and ASCII measurements list interfaces can be concurrently open by multiple readers, or alternatively by a single writer. A semaphore cannot be used because the kernel cannot return to user space with a lock held. Introduce the ima_measure_lock() and ima_measure_unlock() primitives, to respectively lock/unlock the interfaces (safely with the ima_measure_users counter, without holding a lock). Finally, introduce _ima_measurements_open() to lock the interface before seq_open(), and call it from ima_measurements_open() and ima_ascii_measurements_open(). And, introduce ima_measurements_release(), to unlock the interface. Require CAP_SYS_ADMIN if the interface is opened for write (not possible for the current measurements interfaces, since they only have read permission). No functional changes: multiple readers are allowed as before. Link: https://github.com/linux-integrity/linux/issues/1 Signed-off-by: Roberto Sassu --- security/integrity/ima/ima_fs.c | 71 +++++++++++++++++++++++++++++++-- 1 file changed, 67 insertions(+), 4 deletions(-) diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_f= s.c index 9a8dba14d82a..68edea7139d5 100644 --- a/security/integrity/ima/ima_fs.c +++ b/security/integrity/ima/ima_fs.c @@ -25,6 +25,8 @@ #include "ima.h" =20 static DEFINE_MUTEX(ima_write_mutex); +static DEFINE_MUTEX(ima_measure_mutex); +static long ima_measure_users; =20 bool ima_canonical_fmt; static int __init default_canonical_fmt_setup(char *str) @@ -209,16 +211,76 @@ static const struct seq_operations ima_measurments_se= qops =3D { .show =3D ima_measurements_show }; =20 +static int ima_measure_lock(bool write) +{ + mutex_lock(&ima_measure_mutex); + if ((write && ima_measure_users !=3D 0) || + (!write && ima_measure_users < 0)) { + mutex_unlock(&ima_measure_mutex); + return -EBUSY; + } + + if (write) + ima_measure_users--; + else + ima_measure_users++; + mutex_unlock(&ima_measure_mutex); + return 0; +} + +static void ima_measure_unlock(bool write) +{ + mutex_lock(&ima_measure_mutex); + if (write) + ima_measure_users++; + else + ima_measure_users--; + mutex_unlock(&ima_measure_mutex); +} + +static int _ima_measurements_open(struct inode *inode, struct file *file, + const struct seq_operations *seq_ops) +{ + bool write =3D (file->f_mode & FMODE_WRITE); + int ret; + + if (write && !capable(CAP_SYS_ADMIN)) + return -EPERM; + + ret =3D ima_measure_lock(write); + if (ret < 0) + return ret; + + ret =3D seq_open(file, seq_ops); + if (ret < 0) + ima_measure_unlock(write); + + return ret; +} + static int ima_measurements_open(struct inode *inode, struct file *file) { - return seq_open(file, &ima_measurments_seqops); + return _ima_measurements_open(inode, file, &ima_measurments_seqops); +} + +static int ima_measurements_release(struct inode *inode, struct file *file) +{ + bool write =3D (file->f_mode & FMODE_WRITE); + int ret; + + /* seq_release() always returns zero. */ + ret =3D seq_release(inode, file); + + ima_measure_unlock(write); + + return ret; } =20 static const struct file_operations ima_measurements_ops =3D { .open =3D ima_measurements_open, .read =3D seq_read, .llseek =3D seq_lseek, - .release =3D seq_release, + .release =3D ima_measurements_release, }; =20 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size) @@ -283,14 +345,15 @@ static const struct seq_operations ima_ascii_measurem= ents_seqops =3D { =20 static int ima_ascii_measurements_open(struct inode *inode, struct file *f= ile) { - return seq_open(file, &ima_ascii_measurements_seqops); + return _ima_measurements_open(inode, file, + &ima_ascii_measurements_seqops); } =20 static const struct file_operations ima_ascii_measurements_ops =3D { .open =3D ima_ascii_measurements_open, .read =3D seq_read, .llseek =3D seq_lseek, - .release =3D seq_release, + .release =3D ima_measurements_release, }; =20 static ssize_t ima_read_policy(char *path) --=20 2.43.0