[RFC PATCH v8 10/17] block|security: add LSM blob to block_device
Casey Schaufler
casey at schaufler-ca.com
Wed Jun 8 20:07:39 UTC 2022
On 6/8/2022 12:01 PM, Deven Bowers wrote:
> 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 at linux.microsoft.com>
Reviewed-by: Casey Schaufler <casey at schaufler-ca.com>
Not everyone is going to appreciate the infrastructure allocation
of the block_device security blob, but I do.
>
> ---
> v2:
> + No Changes
>
> v3:
> + Minor style changes from checkpatch --strict
>
> v4:
> + No Changes
>
> v5:
> + Allow multiple callers to call security_bdev_setsecurity
>
> v6:
> + Simplify security_bdev_setsecurity break condition
>
> v7:
> + Squash all dm-verity related patches to two patches,
> the additions to dm-verity/fs, and the consumption of
> the additions.
>
> v8:
> + Split dm-verity related patches squashed in v7 to 3 commits based on
> topic:
> + New LSM hook
> + Consumption of hook outside LSM
> + Consumption of hook inside LSM.
>
> + change return of security_bdev_alloc / security_bdev_setsecurity
> to LSM_RET_DEFAULT instead of 0.
>
> + Change return code to -EOPNOTSUPP, bring inline with other
> setsecurity hooks.
> ---
> block/bdev.c | 7 ++++
> include/linux/blk_types.h | 1 +
> 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, 117 insertions(+)
>
> diff --git a/block/bdev.c b/block/bdev.c
> index 5fe06c1f2def..e7ef2c7a22c9 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 "../fs/internal.h"
> @@ -397,6 +398,11 @@ static struct inode *bdev_alloc_inode(struct super_block *sb)
> if (!ei)
> return NULL;
> memset(&ei->bdev, 0, sizeof(ei->bdev));
> +
> + if (unlikely(security_bdev_alloc(&ei->bdev))) {
> + kmem_cache_free(bdev_cachep, ei);
> + return NULL;
> + }
> return &ei->vfs_inode;
> }
>
> @@ -406,6 +412,7 @@ 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 a24d4078fb21..a014ffa14b2d 100644
> --- a/include/linux/blk_types.h
> +++ b/include/linux/blk_types.h
> @@ -68,6 +68,7 @@ struct block_device {
> #ifdef CONFIG_FAIL_MAKE_REQUEST
> bool bd_make_it_fail;
> #endif
> + void *security;
> } __randomize_layout;
>
> #define bdev_whole(_bdev) \
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index eafa1d2489fd..3449c004bd84 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -407,3 +407,8 @@ LSM_HOOK(int, 0, perf_event_write, struct perf_event *event)
> LSM_HOOK(int, 0, uring_override_creds, const struct cred *new)
> LSM_HOOK(int, 0, uring_sqpoll, void)
> #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 91c8146649f5..9f011d705ea8 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -1550,6 +1550,17 @@
> *
> * @what: kernel feature being accessed
> *
> + * @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.
> + *
> * Security hooks for perf events
> *
> * @perf_event_open:
> @@ -1610,6 +1621,7 @@ struct lsm_blob_sizes {
> int lbs_ipc;
> int lbs_msg_msg;
> int lbs_task;
> + int lbs_bdev;
> };
>
> /*
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 7fc4e9f49f54..30b663de301f 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -473,6 +473,11 @@ int security_inode_notifysecctx(struct inode *inode, void *ctx, u32 ctxlen);
> int security_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen);
> int security_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen);
> int security_locked_down(enum lockdown_reason what);
> +int security_bdev_alloc(struct block_device *bdev);
> +void security_bdev_free(struct block_device *bdev);
> +int security_bdev_setsecurity(struct block_device *bdev,
> + const char *name, const void *value,
> + size_t size);
> #else /* CONFIG_SECURITY */
>
> static inline int call_blocking_lsm_notifier(enum lsm_event event, void *data)
> @@ -1349,6 +1354,23 @@ static inline int security_locked_down(enum lockdown_reason what)
> {
> return 0;
> }
> +
> +static inline int security_bdev_alloc(struct block_device *bdev)
> +{
> + return 0;
> +}
> +
> +static inline void security_bdev_free(struct block_device *bdev)
> +{
> +}
> +
> +static inline int security_bdev_setsecurity(struct block_device *bdev,
> + const char *name,
> + const void *value, size_t size)
> +{
> + return 0;
> +}
> +
> #endif /* CONFIG_SECURITY */
>
> #if defined(CONFIG_SECURITY) && defined(CONFIG_WATCH_QUEUE)
> diff --git a/security/security.c b/security/security.c
> index 188b8f782220..59ec336788e8 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -29,6 +29,7 @@
> #include <linux/string.h>
> #include <linux/msg.h>
> #include <net/flow.h>
> +#include <linux/fs.h>
>
> #define MAX_LSM_EVM_XATTR 2
>
> @@ -208,6 +209,7 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
> lsm_set_blob_size(&needed->lbs_msg_msg, &blob_sizes.lbs_msg_msg);
> lsm_set_blob_size(&needed->lbs_superblock, &blob_sizes.lbs_superblock);
> lsm_set_blob_size(&needed->lbs_task, &blob_sizes.lbs_task);
> + lsm_set_blob_size(&needed->lbs_bdev, &blob_sizes.lbs_bdev);
> }
>
> /* Prepare LSM for initialization. */
> @@ -344,6 +346,7 @@ static void __init ordered_lsm_init(void)
> init_debug("msg_msg blob size = %d\n", blob_sizes.lbs_msg_msg);
> init_debug("superblock blob size = %d\n", blob_sizes.lbs_superblock);
> init_debug("task blob size = %d\n", blob_sizes.lbs_task);
> + init_debug("bdev blob size = %d\n", blob_sizes.lbs_bdev);
>
> /*
> * Create any kmem_caches needed for blobs
> @@ -660,6 +663,28 @@ static int lsm_msg_msg_alloc(struct msg_msg *mp)
> return 0;
> }
>
> +/**
> + * lsm_bdev_alloc - allocate a composite block_device blob
> + * @bdev: the block_device that needs a blob
> + *
> + * Allocate the block_device blob for all the modules
> + *
> + * Returns 0, or -ENOMEM if memory can't be allocated.
> + */
> +static int lsm_bdev_alloc(struct block_device *bdev)
> +{
> + if (blob_sizes.lbs_bdev == 0) {
> + bdev->security = NULL;
> + return 0;
> + }
> +
> + bdev->security = kzalloc(blob_sizes.lbs_bdev, GFP_KERNEL);
> + if (!bdev->security)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> /**
> * lsm_early_task - during initialization allocate a composite task blob
> * @task: the task that needs a blob
> @@ -2617,6 +2642,51 @@ 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);
> +
> #ifdef CONFIG_PERF_EVENTS
> int security_perf_event_open(struct perf_event_attr *attr, int type)
> {
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