From patchwork Sat Apr 13 00:55:48 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fan Wu X-Patchwork-Id: 13628515 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 2867DD272; Sat, 13 Apr 2024 00:56:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712969770; cv=none; b=fyNaWwaAp8infCAEYeJqiQBe4QRRLvS8OTdpxak1Cqyb8QFseHDzciEGuDGyYLoEGZDlXOFRlVHZLN8/Z1zJ8YGDX5HoIXyQVADPU/xfP3Hgz6GqoVURk1aJ/3bRMRpvY2qRVtPYs4kDqSQodVGNDFffAKlRg5daQiq32jzsouw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712969770; c=relaxed/simple; bh=m5Kz6kJ4CrfXX6/Z5HMC0WcjyIrA1GmlYuyeYtJlPUs=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References; b=ehn4561txRZ3Wnr6hPtTJD4pT/N8z0enBWAsqZ4bhdGb5mdUGehCFJIn2fuSzTFUOPjvs5Ka1cmextrGEYXw2b8AAMrmFHgpwOz9MwcPg7azactumW7iPKLQhLmwmExVUSZ9HH46IrFJYnEZlNgZ972iuNCQoLWFAzeKBqfEI1c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=WFNjQuOg; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="WFNjQuOg" Received: by linux.microsoft.com (Postfix, from userid 1052) id BD1D620F32BE; Fri, 12 Apr 2024 17:56:05 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com BD1D620F32BE DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1712969765; bh=CBTFK3KrsGTrn+prErhAJwRVbssSwYdjlBDBKa+A8D4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WFNjQuOgT1a1n3gXogI2Xbc1we2gO7L+g8jTdOWyrjP5EYMlEwUxfztQxpDZIk/Jb UDFStxSWQdQ1yv5R1aGSoXPfMNtpF6VxPHPck78yADdS+RLZbGuC3j62mghOEsPVXe 0BOnVPTFttWX0nRP+MnnTX1OV7UWpVbKEaJKRIJU= From: Fan Wu To: corbet@lwn.net, zohar@linux.ibm.com, jmorris@namei.org, serge@hallyn.com, tytso@mit.edu, ebiggers@kernel.org, axboe@kernel.dk, agk@redhat.com, snitzer@kernel.org, eparis@redhat.com, paul@paul-moore.com Cc: linux-doc@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, fsverity@lists.linux.dev, linux-block@vger.kernel.org, dm-devel@lists.linux.dev, audit@vger.kernel.org, linux-kernel@vger.kernel.org, Fan Wu Subject: [PATCH v17 05/21] initramfs|security: Add a security hook to do_populate_rootfs() Date: Fri, 12 Apr 2024 17:55:48 -0700 Message-Id: <1712969764-31039-6-git-send-email-wufan@linux.microsoft.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1712969764-31039-1-git-send-email-wufan@linux.microsoft.com> References: <1712969764-31039-1-git-send-email-wufan@linux.microsoft.com> Precedence: bulk X-Mailing-List: fsverity@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: This patch introduces a new hook to notify security system that the content of initramfs has been unpacked into the rootfs. Upon receiving this notification, the security system can activate a policy to allow only files that originated from the initramfs to execute or load into kernel during the early stages of booting. This approach is crucial for minimizing the attack surface by ensuring that only trusted files from the initramfs are operational in the critical boot phase. Signed-off-by: Fan Wu --- v1-v11: + Not present v12: + Introduced v13: + Rename the hook name to initramfs_populated() v14: + No changes v15: + No changes v16: + No changes v17: + Fix ocumentation style issues --- include/linux/lsm_hook_defs.h | 2 ++ include/linux/security.h | 8 ++++++++ init/initramfs.c | 3 +++ security/security.c | 10 ++++++++++ 4 files changed, 23 insertions(+) diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 334e00efbde4..7db99ae75651 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -450,3 +450,5 @@ LSM_HOOK(int, 0, uring_override_creds, const struct cred *new) LSM_HOOK(int, 0, uring_sqpoll, void) LSM_HOOK(int, 0, uring_cmd, struct io_uring_cmd *ioucmd) #endif /* CONFIG_IO_URING */ + +LSM_HOOK(void, LSM_RET_VOID, initramfs_populated, void) diff --git a/include/linux/security.h b/include/linux/security.h index 41a8f667bdfa..14fff542f2e3 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -2255,4 +2255,12 @@ static inline int security_uring_cmd(struct io_uring_cmd *ioucmd) #endif /* CONFIG_SECURITY */ #endif /* CONFIG_IO_URING */ +#ifdef CONFIG_SECURITY +extern void security_initramfs_populated(void); +#else +static inline void security_initramfs_populated(void) +{ +} +#endif /* CONFIG_SECURITY */ + #endif /* ! __LINUX_SECURITY_H */ diff --git a/init/initramfs.c b/init/initramfs.c index a298a3854a80..feedb47d0f55 100644 --- a/init/initramfs.c +++ b/init/initramfs.c @@ -17,6 +17,7 @@ #include #include #include +#include #include "do_mounts.h" @@ -719,6 +720,8 @@ static void __init do_populate_rootfs(void *unused, async_cookie_t cookie) #endif } + security_initramfs_populated(); + done: /* * If the initrd region is overlapped with crashkernel reserved region, diff --git a/security/security.c b/security/security.c index 820e0d437452..0db5a6b32aab 100644 --- a/security/security.c +++ b/security/security.c @@ -5675,3 +5675,13 @@ int security_uring_cmd(struct io_uring_cmd *ioucmd) return call_int_hook(uring_cmd, ioucmd); } #endif /* CONFIG_IO_URING */ + +/** + * security_initramfs_populated() - Notify LSMs that initramfs has been loaded + * + * Tells the LSMs the initramfs has been unpacked into the rootfs. + */ +void security_initramfs_populated(void) +{ + call_void_hook(initramfs_populated); +}