[RFC PATCH v6 05/11] fs: add security blob and hooks for block_device

Deven Bowers
2020-07-30T00:32:25Z

Add a security blob and associated allocation, deallocation and set hooks
for a block_device structure.

Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
---
fs/block_dev.c | 8 ++++
include/linux/fs.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, 118 insertions(+)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 0ae656e022fd..8602dd62c3e2 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -34,6 +34,7 @@
#include <linux/falloc.h>
#include <linux/uaccess.h>
#include <linux/suspend.h>
+#include <linux/security.h>
#include "internal.h"

struct bdev_inode {
@@ -768,11 +769,18 @@ static struct inode *bdev_alloc_inode(struct super_block *sb)
struct bdev_inode *ei = kmem_cache_alloc(bdev_cachep, GFP_KERNEL);
if (!ei)
return NULL;
+
+ if (unlikely(security_bdev_alloc(&ei->bdev))) {
+ kmem_cache_free(bdev_cachep, ei);
+ return NULL;
+ }
+
return &ei->vfs_inode;
}

static void bdev_free_inode(struct inode *inode)
{
+ security_bdev_free(&BDEV_I(inode)->bdev);
kmem_cache_free(bdev_cachep, BDEV_I(inode));
}

diff --git a/include/linux/fs.h b/include/linux/fs.h
index f5abba86107d..42d7e3ce7712 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -509,6 +509,7 @@ struct block_device {
int bd_fsfreeze_count;
/* Mutex for freeze */
struct mutex bd_fsfreeze_mutex;
+ void *security;
} __randomize_layout;

/* XArray tags, for tagging dirty and writeback pages in the pagecache. */
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index af998f93d256..f3c0da0db4e8 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -391,3 +391,8 @@ LSM_HOOK(void, LSM_RET_VOID, perf_event_free, struct perf_event *event)
LSM_HOOK(int, 0, perf_event_read, struct perf_event *event)
LSM_HOOK(int, 0, perf_event_write, struct perf_event *event)
#endif /* CONFIG_PERF_EVENTS */
+
+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 95b7c1d32062..8670c19a8cef 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1507,6 +1507,17 @@
*
* @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 -ENOSYS.
+ *
* Security hooks for perf events
*
* @perf_event_open:
@@ -1553,6 +1564,7 @@ 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 0a0a03b36a3b..8f83fdc6c65d 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -451,6 +451,11 @@ 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)
@@ -1291,6 +1296,23 @@ 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 70a7ad357bc6..de523b0d8f56 100644
--- a/security/security.c
+++ b/security/security.c
@@ -28,6 +28,7 @@
#include <linux/string.h>
#include <linux/msg.h>
#include <net/flow.h>
+#include <linux/fs.h>

#define MAX_LSM_EVM_XATTR 2

@@ -202,6 +203,7 @@ static void __init lsm_set_blob_sizes(struct lsm_blob_sizes *needed)
lsm_set_blob_size(&needed->lbs_ipc, &blob_sizes.lbs_ipc);
lsm_set_blob_size(&needed->lbs_msg_msg, &blob_sizes.lbs_msg_msg);
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. */
@@ -337,6 +339,7 @@ static void __init ordered_lsm_init(void)
init_debug("ipc blob size = %d\n", blob_sizes.lbs_ipc);
init_debug("msg_msg blob size = %d\n", blob_sizes.lbs_msg_msg);
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
@@ -654,6 +657,28 @@ 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
@@ -2516,6 +2541,51 @@ 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 0;
+}
+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 != -ENOSYS)
+ return rc;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(security_bdev_setsecurity);
+
#ifdef CONFIG_PERF_EVENTS
int security_perf_event_open(struct perf_event_attr *attr, int type)
{
--
2.27.0