firmware: replace call to fw_read_file_contents() with kernel version

Replace the fw_read_file_contents with kernel_file_read_from_path().

Although none of the upstreamed LSMs define a kernel_fw_from_file hook,
IMA is called by the security function to prevent unsigned firmware from
being loaded and to measure/appraise signed firmware, based on policy.

Instead of reading the firmware twice, once for measuring/appraising the
firmware and again for reading the firmware contents into memory, the
kernel_post_read_file() security hook calculates the file hash based on
the in memory file buffer.  The firmware is read once.

This patch removes the LSM kernel_fw_from_file() hook and security call.

Changelog v4+:
- revert dropped buf->size assignment - reported by Sergey Senozhatsky
v3:
- remove kernel_fw_from_file hook
- use kernel_file_read_from_path() - requested by Luis
v2:
- reordered and squashed firmware patches
- fix MAX firmware size (Kees Cook)

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Luis R. Rodriguez <mcgrof@kernel.org>

4 files changed, 1 insertions, 24 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 00fa5c45fd63..c8bc4d8c843f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2577,6 +2577,7 @@ static inline void i_readcount_inc(struct inode *inode)
 extern int do_pipe_flags(int *, int);
 
 enum kernel_read_file_id {
+	READING_FIRMWARE = 1,
 	READING_MAX_ID
 };
 
diff --git a/include/linux/ima.h b/include/linux/ima.h
index d29a6a23fc19..7aea4863c244 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -19,7 +19,6 @@ extern int ima_file_check(struct file *file, int mask, int opened);
 extern void ima_file_free(struct file *file);
 extern int ima_file_mmap(struct file *file, unsigned long prot);
 extern int ima_module_check(struct file *file);
-extern int ima_fw_from_file(struct file *file, char *buf, size_t size);
 extern int ima_post_read_file(struct file *file, void *buf, loff_t size,
 			      enum kernel_read_file_id id);
 
@@ -49,11 +48,6 @@ static inline int ima_module_check(struct file *file)
 	return 0;
 }
 
-static inline int ima_fw_from_file(struct file *file, char *buf, size_t size)
-{
-	return 0;
-}
-
 static inline int ima_post_read_file(struct file *file, void *buf, loff_t size,
 				     enum kernel_read_file_id id)
 {
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 2337f33913c1..7d04a1220223 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -541,15 +541,6 @@
  *	@inode points to the inode to use as a reference.
  *	The current task must be the one that nominated @inode.
  *	Return 0 if successful.
- * @kernel_fw_from_file:
- *	Load firmware from userspace (not called for built-in firmware).
- *	@file contains the file structure pointing to the file containing
- *	the firmware to load. This argument will be NULL if the firmware
- *	was loaded via the uevent-triggered blob-based interface exposed
- *	by CONFIG_FW_LOADER_USER_HELPER.
- *	@buf pointer to buffer containing firmware contents.
- *	@size length of the firmware contents.
- *	Return 0 if permission is granted.
  * @kernel_module_request:
  *	Ability to trigger the kernel to automatically upcall to userspace for
  *	userspace to load a kernel module with the given name.
@@ -1462,7 +1453,6 @@ union security_list_options {
 	void (*cred_transfer)(struct cred *new, const struct cred *old);
 	int (*kernel_act_as)(struct cred *new, u32 secid);
 	int (*kernel_create_files_as)(struct cred *new, struct inode *inode);
-	int (*kernel_fw_from_file)(struct file *file, char *buf, size_t size);
 	int (*kernel_module_request)(char *kmod_name);
 	int (*kernel_module_from_file)(struct file *file);
 	int (*kernel_post_read_file)(struct file *file, char *buf, loff_t size,
@@ -1725,7 +1715,6 @@ struct security_hook_heads {
 	struct list_head cred_transfer;
 	struct list_head kernel_act_as;
 	struct list_head kernel_create_files_as;
-	struct list_head kernel_fw_from_file;
 	struct list_head kernel_post_read_file;
 	struct list_head kernel_module_request;
 	struct list_head kernel_module_from_file;
diff --git a/include/linux/security.h b/include/linux/security.h
index d920718dc845..cee1349e1155 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -300,7 +300,6 @@ int security_prepare_creds(struct cred *new, const struct cred *old, gfp_t gfp);
 void security_transfer_creds(struct cred *new, const struct cred *old);
 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_fw_from_file(struct file *file, char *buf, size_t size);
 int security_kernel_module_request(char *kmod_name);
 int security_kernel_module_from_file(struct file *file);
 int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
@@ -854,12 +853,6 @@ static inline int security_kernel_create_files_as(struct cred *cred,
 	return 0;
 }
 
-static inline int security_kernel_fw_from_file(struct file *file,
-					       char *buf, size_t size)
-{
-	return 0;
-}
-
 static inline int security_kernel_module_request(char *kmod_name)
 {
 	return 0;