[RFC,v3,05/12] fs: add security blob and hooks for block_device
diff mbox series

Message ID 20200415162550.2324-6-deven.desai@linux.microsoft.com
State New
Headers show
Series
  • Integrity Policy Enforcement LSM (IPE)
Related show

Commit Message

Deven Bowers April 15, 2020, 4:25 p.m. UTC
From: Deven Bowers <deven.desai@linux.microsoft.com>

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     | 11 +++++++
 include/linux/security.h      | 22 +++++++++++++
 security/security.c           | 61 +++++++++++++++++++++++++++++++++++
 6 files changed, 108 insertions(+)

Comments

James Morris April 22, 2020, 4:42 p.m. UTC | #1
On Wed, 15 Apr 2020, deven.desai@linux.microsoft.com wrote:

> From: Deven Bowers <deven.desai@linux.microsoft.com>
> 
> 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>

Is there any feedback from block or LSM folk on the addition of a security 
blob for block_device here?

IPE uses this is to track the status of integrity verification of e.g. 
DM-Verity devices, per this code from a subsequent patch:


+       ret = security_bdev_setsecurity(dm_table_get_md(v->ti->table)->bdev,
+                                       DM_VERITY_SIGNATURE_SEC_NAME,
+                                       v->sig->sig, v->sig->sig_size);
Casey Schaufler April 22, 2020, 4:55 p.m. UTC | #2
On 4/22/2020 9:42 AM, James Morris wrote:
> On Wed, 15 Apr 2020, deven.desai@linux.microsoft.com wrote:
>
>> From: Deven Bowers <deven.desai@linux.microsoft.com>
>>
>> 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>
> Is there any feedback from block or LSM folk on the addition of a security 
> blob for block_device here?

The addition of a blob looks to have been done correctly.
As for it's use, I haven't had the chance to review the patches that
use it. I didn't see a patch that implements the hooks in a LSM,
but that could just be me. 

>
> IPE uses this is to track the status of integrity verification of e.g. 
> DM-Verity devices, per this code from a subsequent patch:
>
>
> +       ret = security_bdev_setsecurity(dm_table_get_md(v->ti->table)->bdev,
> +                                       DM_VERITY_SIGNATURE_SEC_NAME,
> +                                       v->sig->sig, v->sig->sig_size);
>
>

Patch
diff mbox series

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 52b6f646cdbd..5dfa25f03208 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -35,6 +35,7 @@ 
 #include <linux/falloc.h>
 #include <linux/uaccess.h>
 #include <linux/suspend.h>
+#include <linux/security.h>
 #include "internal.h"
 
 struct bdev_inode {
@@ -773,11 +774,18 @@  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 4f6f59b4f22a..9ed0060c5a91 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -506,6 +506,7 @@  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 9cd4455528e5..4782fef7eaf9 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -379,3 +379,8 @@  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 988ca0df7824..7bf0f82bc5d6 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -1476,6 +1476,16 @@ 
  *
  *     @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 the security property associated with @name for @bdev with
+ *	value @value. @size indicates the size of the @value in bytes.
+ *
  * Security hooks for perf events
  *
  * @perf_event_open:
@@ -1522,6 +1532,7 @@  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 a8d9310472df..714eecc82e08 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -446,6 +446,11 @@  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)
@@ -1273,6 +1278,23 @@  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 */
 
 #ifdef CONFIG_SECURITY_NETWORK
diff --git a/security/security.c b/security/security.c
index 7fed24b9d57e..0d1af27711c1 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
@@ -2456,6 +2481,42 @@  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)
+{
+	return call_int_hook(bdev_setsecurity, 0, bdev, name, value, size);
+}
+EXPORT_SYMBOL(security_bdev_setsecurity);
+
 #ifdef CONFIG_PERF_EVENTS
 int security_perf_event_open(struct perf_event_attr *attr, int type)
 {