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Message-ID: <CAHC9VhTiLafboxni2z01mxs=QNZFjgJ7EMJL33RWPpTqJKgfgA@mail.gmail.com>
Date: Thu, 2 Mar 2023 14:07:27 -0500
From: Paul Moore <paul@...l-moore.com>
To: Fan Wu <wufan@...ux.microsoft.com>
Cc: corbet@....net, zohar@...ux.ibm.com, jmorris@...ei.org,
serge@...lyn.com, tytso@....edu, ebiggers@...nel.org,
axboe@...nel.dk, agk@...hat.com, snitzer@...nel.org,
eparis@...hat.com, linux-doc@...r.kernel.org,
linux-integrity@...r.kernel.org,
linux-security-module@...r.kernel.org,
linux-fscrypt@...r.kernel.org, linux-block@...r.kernel.org,
dm-devel@...hat.com, linux-audit@...hat.com,
roberto.sassu@...wei.com, linux-kernel@...r.kernel.org,
Deven Bowers <deven.desai@...ux.microsoft.com>
Subject: Re: [RFC PATCH v9 09/16] block|security: add LSM blob to block_device
On Mon, Jan 30, 2023 at 5:58 PM Fan Wu <wufan@...ux.microsoft.com> wrote:
>
> From: Deven Bowers <deven.desai@...ux.microsoft.com>
>
> block_device structures can have valuable security properties,
> based on how they are created, and what subsystem manages them.
>
> By adding LSM storage to this structure, this data can be accessed
> at the LSM layer.
>
> Signed-off-by: Deven Bowers <deven.desai@...ux.microsoft.com>
> Signed-off-by: Fan Wu <wufan@...ux.microsoft.com>
> Reviewed-by: Casey Schaufler <casey@...aufler-ca.com>
...
> ---
> block/bdev.c | 7 ++++
> include/linux/blk_types.h | 3 ++
> include/linux/lsm_hook_defs.h | 5 +++
> include/linux/lsm_hooks.h | 12 ++++++
> include/linux/security.h | 22 +++++++++++
> security/security.c | 70 +++++++++++++++++++++++++++++++++++
> 6 files changed, 119 insertions(+)
>
> diff --git a/block/bdev.c b/block/bdev.c
> index edc110d90df4..f8db53b47c00 100644
> --- a/block/bdev.c
> +++ b/block/bdev.c
> @@ -24,6 +24,7 @@
> #include <linux/pseudo_fs.h>
> #include <linux/uio.h>
> #include <linux/namei.h>
> +#include <linux/security.h>
> #include <linux/part_stat.h>
> #include <linux/uaccess.h>
> #include <linux/stat.h>
> @@ -396,6 +397,11 @@ static struct inode *bdev_alloc_inode(struct super_block *sb)
> if (!ei)
> return NULL;
> memset(&ei->bdev, 0, sizeof(ei->bdev));
> +
> + if (security_bdev_alloc(&ei->bdev)) {
> + kmem_cache_free(bdev_cachep, ei);
> + return NULL;
> + }
> return &ei->vfs_inode;
> }
>
> @@ -405,6 +411,7 @@ static void bdev_free_inode(struct inode *inode)
>
> free_percpu(bdev->bd_stats);
> kfree(bdev->bd_meta_info);
> + security_bdev_free(bdev);
>
> if (!bdev_is_partition(bdev)) {
> if (bdev->bd_disk && bdev->bd_disk->bdi)
> diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
> index 99be590f952f..137a04f45c17 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -68,6 +68,9 @@ struct block_device {
> #ifdef CONFIG_FAIL_MAKE_REQUEST
> bool bd_make_it_fail;
> #endif
> +#ifdef CONFIG_SECURITY
> + void *security;
> +#endif
> } __randomize_layout;
>
> #define bdev_whole(_bdev) \
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index ed6cb2ac55fa..1f79029c9e28 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -417,3 +417,8 @@ 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(int, 0, bdev_alloc_security, struct block_device *bdev)
> +LSM_HOOK(void, LSM_RET_VOID, bdev_free_security, struct block_device *bdev)
> +LSM_HOOK(int, 0, bdev_setsecurity, struct block_device *bdev, const char *name,
> + const void *value, size_t size)
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 0a5ba81f7367..b622ceb57d83 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1618,6 +1618,17 @@
> * @what: kernel feature being accessed.
> * Return 0 if permission is granted.
> *
> + * @bdev_alloc_security:
> + * Initialize the security field inside a block_device structure.
> + *
> + * @bdev_free_security:
> + * Cleanup the security information stored inside a block_device structure.
> + *
> + * @bdev_setsecurity:
> + * Set a security property associated with @name for @bdev with
> + * value @value. @size indicates the size of @value in bytes.
> + * If a @name is not implemented, return -EOPNOTSUPP.
> + *
Just a heads-up that the LSM hook comment blocks are moving to
security/security.c very soon now (if they are not already there by
the time you read this).
https://lore.kernel.org/linux-security-module/20230217032625.678457-1-paul@paul-moore.com
> diff --git a/security/security.c b/security/security.c
> index d1571900a8c7..5c81dd3b1350 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2705,6 +2730,51 @@ int security_locked_down(enum lockdown_reason what)
> }
> EXPORT_SYMBOL(security_locked_down);
>
> +int security_bdev_alloc(struct block_device *bdev)
> +{
> + int rc = 0;
> +
> + rc = lsm_bdev_alloc(bdev);
> + if (unlikely(rc))
> + return rc;
> +
> + rc = call_int_hook(bdev_alloc_security, 0, bdev);
> + if (unlikely(rc))
> + security_bdev_free(bdev);
> +
> + return LSM_RET_DEFAULT(bdev_alloc_security);
> +}
> +EXPORT_SYMBOL(security_bdev_alloc);
> +
> +void security_bdev_free(struct block_device *bdev)
> +{
> + if (!bdev->security)
> + return;
> +
> + call_void_hook(bdev_free_security, bdev);
> +
> + kfree(bdev->security);
> + bdev->security = NULL;
> +}
> +EXPORT_SYMBOL(security_bdev_free);
> +
> +int security_bdev_setsecurity(struct block_device *bdev,
> + const char *name, const void *value,
> + size_t size)
> +{
> + int rc = 0;
> + struct security_hook_list *p;
> +
> + hlist_for_each_entry(p, &security_hook_heads.bdev_setsecurity, list) {
> + rc = p->hook.bdev_setsecurity(bdev, name, value, size);
> + if (rc && rc != -EOPNOTSUPP)
> + return rc;
> + }
> +
> + return LSM_RET_DEFAULT(bdev_setsecurity);
> +}
> +EXPORT_SYMBOL(security_bdev_setsecurity);
I think we need to see the `security_bdev_setsecurity()` hook actually
used by a caller in this patch.
> #ifdef CONFIG_PERF_EVENTS
> int security_perf_event_open(struct perf_event_attr *attr, int type)
> {
> --
> 2.39.0
--
paul-moore.com
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