Re: [PATCH v5 1/8] security: define new LSM hook named security_kernel_load_data

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On 7/2/18 7:37 AM, Mimi Zohar wrote:
Differentiate between the kernel reading a file from the kernel loading
data provided by userspace.  This patch defines a new LSM hook named
security_kernel_load_data.

If this patch series is re-done, can we tweak the description here please?  From what I understood of the code in this patch, I'd tweak it as:

"Differentiate between the kernel reading a file specified by userspace and the kernel loading a block of data provided by userspace.  This patch defines a new LSM hook named security_kernel_load_data()."

From the description, I got a tad confused if the the kernel reading a file was also provided by userspace (I know it may be 2nd-nature to people on this list, I'm still learning this kernel module).

Thanks,
Jay

Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Luis R. Rodriguez <mcgrof@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Acked-by: Serge Hallyn <serge@xxxxxxxxxx>

---
Changelog v5:
- Share the kernel_load_data_id and kernel_read_file_id values,
simplifying Loadpin's and other LSMs calling one LSM hook from the
other.

Changelog v4:
- Define new LSM hook named security_kernel_load_data.

Changelog v3:
- Rename security_kernel_read_file to security_kernel_read_data().

Changelog v2:
- Define a generic wrapper named security_kernel_read_blob() for
security_kernel_read_file().

Changelog v1:
- Define and call security_kexec_load(), a wrapper for
security_kernel_read_file().

  include/linux/lsm_hooks.h |  6 ++++++
  include/linux/security.h  | 27 +++++++++++++++++++++++++++
  security/security.c       |  5 +++++
  3 files changed, 38 insertions(+)

diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 8f1131c8dd54..a08bc2587b96 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -576,6 +576,10 @@
   *	userspace to load a kernel module with the given name.
   *	@kmod_name name of the module requested by the kernel
   *	Return 0 if successful.
+ * @kernel_load_data:
+ *	Load data provided by userspace.
+ *	@id kernel load data identifier
+ *	Return 0 if permission is granted.
   * @kernel_read_file:
   *	Read a file specified by userspace.
   *	@file contains the file structure pointing to the file being read
@@ -1582,6 +1586,7 @@ union security_list_options {
  	int (*kernel_act_as)(struct cred *new, u32 secid);
  	int (*kernel_create_files_as)(struct cred *new, struct inode *inode);
  	int (*kernel_module_request)(char *kmod_name);
+	int (*kernel_load_data)(enum kernel_load_data_id id);
  	int (*kernel_read_file)(struct file *file, enum kernel_read_file_id id);
  	int (*kernel_post_read_file)(struct file *file, char *buf, loff_t size,
  				     enum kernel_read_file_id id);
@@ -1872,6 +1877,7 @@ struct security_hook_heads {
  	struct hlist_head cred_getsecid;
  	struct hlist_head kernel_act_as;
  	struct hlist_head kernel_create_files_as;
+	struct hlist_head kernel_load_data;
  	struct hlist_head kernel_read_file;
  	struct hlist_head kernel_post_read_file;
  	struct hlist_head kernel_module_request;
diff --git a/include/linux/security.h b/include/linux/security.h
index 63030c85ee19..3410acfe139c 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -159,6 +159,27 @@ extern int mmap_min_addr_handler(struct ctl_table *table, int write,
  typedef int (*initxattrs) (struct inode *inode,
  			   const struct xattr *xattr_array, void *fs_data);
+
+/* Keep the kernel_load_data_id enum in sync with kernel_read_file_id */
+#define __data_id_enumify(ENUM, dummy) LOADING_ ## ENUM,
+#define __data_id_stringify(dummy, str) #str,
+
+enum kernel_load_data_id {
+	__kernel_read_file_id(__data_id_enumify)
+};
+
+static const char * const kernel_load_data_str[] = {
+	__kernel_read_file_id(__data_id_stringify)
+};
+
+static inline const char *kernel_load_data_id_str(enum kernel_load_data_id id)
+{
+	if ((unsigned)id >= LOADING_MAX_ID)
+		return kernel_load_data_str[LOADING_UNKNOWN];
+
+	return kernel_load_data_str[id];
+}
+
  #ifdef CONFIG_SECURITY
struct security_mnt_opts {
@@ -320,6 +341,7 @@ void security_cred_getsecid(const struct cred *c, u32 *secid);
  int security_kernel_act_as(struct cred *new, u32 secid);
  int security_kernel_create_files_as(struct cred *new, struct inode *inode);
  int security_kernel_module_request(char *kmod_name);
+int security_kernel_load_data(enum kernel_load_data_id id);
  int security_kernel_read_file(struct file *file, enum kernel_read_file_id id);
  int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
  				   enum kernel_read_file_id id);
@@ -909,6 +931,11 @@ static inline int security_kernel_module_request(char *kmod_name)
  	return 0;
  }
+static inline int security_kernel_load_data(enum kernel_load_data_id id)
+{
+	return 0;
+}
+
  static inline int security_kernel_read_file(struct file *file,
  					    enum kernel_read_file_id id)
  {
diff --git a/security/security.c b/security/security.c
index e7d76a8000a5..05fe5b1932d7 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1061,6 +1061,11 @@ int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
  }
  EXPORT_SYMBOL_GPL(security_kernel_post_read_file);
+int security_kernel_load_data(enum kernel_load_data_id id)
+{
+	return call_int_hook(kernel_load_data, 0, id);
+}
+
  int security_task_fix_setuid(struct cred *new, const struct cred *old,
  			     int flags)
  {




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