From: Casey Schaufler <casey@schaufler-ca.com>
To: Fan Wu <wufan@linux.microsoft.com>,
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,
Casey Schaufler <casey@schaufler-ca.com>
Subject: Re: [RFC PATCH v15 05/21] initramfs|security: Add a security hook to do_populate_rootfs()
Date: Sun, 17 Mar 2024 17:29:14 -0700 [thread overview]
Message-ID: <43958767-32db-4c53-8408-8367cfc14d2f@schaufler-ca.com> (raw)
In-Reply-To: <1710560151-28904-6-git-send-email-wufan@linux.microsoft.com>
On 3/15/2024 8:35 PM, Fan Wu wrote:
> 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 <wufan@linux.microsoft.com>
>
> ---
> v1-v11:
> + Not present
>
> v12:
> + Introduced
>
> v13:
> + Rename the hook name to initramfs_populated()
>
> v14:
> + No changes
>
> v15:
> + No changes
> ---
> 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)
This is an awfully expensive way to set a flag. Adding a LSM hook list
isn't free. Isn't there a way to capture this state change through one of
the mount hooks?
> 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 da79760b8be3..cc9115117896 100644
> --- a/init/initramfs.c
> +++ b/init/initramfs.c
> @@ -17,6 +17,7 @@
> #include <linux/namei.h>
> #include <linux/init_syscalls.h>
> #include <linux/umh.h>
> +#include <linux/security.h>
>
> #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 287bfac6b471..b10230c51c0b 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);
> +}
next prev parent reply other threads:[~2024-03-18 0:29 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-16 3:35 [RFC PATCH v15 00/21] Integrity Policy Enforcement LSM (IPE) Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 01/21] security: add ipe lsm Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 02/21] ipe: add policy parser Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 03/21] ipe: add evaluation loop Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 04/21] ipe: add LSM hooks on execution and kernel read Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 05/21] initramfs|security: Add a security hook to do_populate_rootfs() Fan Wu
2024-03-18 0:29 ` Casey Schaufler [this message]
2024-03-18 1:58 ` Paul Moore
2024-03-16 3:35 ` [RFC PATCH v15 06/21] ipe: introduce 'boot_verified' as a trust provider Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 07/21] security: add new securityfs delete function Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 08/21] ipe: add userspace interface Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 09/21] uapi|audit|ipe: add ipe auditing support Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 10/21] ipe: add permissive toggle Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 11/21] block|security: add LSM blob to block_device Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 12/21] security: add security_bdev_setintegrity() hook Fan Wu
2024-03-19 23:00 ` [PATCH RFC " Paul Moore
2024-03-20 8:28 ` Jarkko Sakkinen
2024-03-20 8:31 ` Jarkko Sakkinen
2024-03-20 20:31 ` Fan Wu
2024-03-21 17:25 ` Jarkko Sakkinen
2024-03-16 3:35 ` [RFC PATCH v15 13/21] dm: add finalize hook to target_type Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 14/21] dm verity: consume root hash digest and signature data via LSM hook Fan Wu
2024-03-19 23:00 ` [PATCH RFC " Paul Moore
2024-03-20 2:19 ` Mike Snitzer
2024-03-20 17:23 ` Paul Moore
2024-03-20 18:49 ` Mike Snitzer
2024-03-20 17:56 ` Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 15/21] ipe: add support for dm-verity as a trust provider Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 16/21] security: add security_inode_setintegrity() hook Fan Wu
2024-03-19 23:00 ` [PATCH RFC " Paul Moore
2024-03-16 3:35 ` [RFC PATCH v15 17/21] fsverity: consume builtin signature via LSM hook Fan Wu
2024-03-18 5:29 ` Eric Biggers
2024-03-19 23:00 ` Paul Moore
2024-03-16 3:35 ` [RFC PATCH v15 18/21] ipe: enable support for fs-verity as a trust provider Fan Wu
2024-03-18 5:17 ` Eric Biggers
2024-03-18 8:08 ` Roberto Sassu
2024-03-18 20:58 ` Fan Wu
2024-03-18 20:40 ` Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 19/21] scripts: add boot policy generation program Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 20/21] ipe: kunit test for parser Fan Wu
2024-03-16 3:35 ` [RFC PATCH v15 21/21] documentation: add ipe documentation Fan Wu
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