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Commit 13752fe2 authored by Kees Cook's avatar Kees Cook
Browse files

security: introduce kernel_fw_from_file hook 



In order to validate the contents of firmware being loaded, there must be
a hook to evaluate any loaded firmware that wasn't built into the kernel
itself. Without this, there is a risk that a root user could load malicious
firmware designed to mount an attack against kernel memory (e.g. via DMA).

Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 7d8b6c63

include/linux/security.h

+17 −0
Original line number Diff line number Diff line
@@ -702,6 +702,15 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts) 
 *	@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.
@@ -1568,6 +1577,7 @@ struct security_operations { 
	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 (*task_fix_setuid) (struct cred *new, const struct cred *old,
@@ -1840,6 +1850,7 @@ 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_task_fix_setuid(struct cred *new, const struct cred *old,
@@ -2366,6 +2377,12 @@ 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;

security/capability.c

+6 −0
Original line number Diff line number Diff line
@@ -401,6 +401,11 @@ static int cap_kernel_create_files_as(struct cred *new, struct inode *inode) 
	return 0;

}



static int cap_kernel_fw_from_file(struct file *file, char *buf, size_t size)

{

	return 0;

}



static int cap_kernel_module_request(char *kmod_name)

{

	return 0;
@@ -1015,6 +1020,7 @@ void __init security_fixup_ops(struct security_operations *ops) 
	set_to_cap_if_null(ops, cred_transfer);

	set_to_cap_if_null(ops, kernel_act_as);

	set_to_cap_if_null(ops, kernel_create_files_as);

	set_to_cap_if_null(ops, kernel_fw_from_file);

	set_to_cap_if_null(ops, kernel_module_request);

	set_to_cap_if_null(ops, kernel_module_from_file);

	set_to_cap_if_null(ops, task_fix_setuid);

security/security.c

+6 −0
Original line number Diff line number Diff line
@@ -845,6 +845,12 @@ int security_kernel_create_files_as(struct cred *new, struct inode *inode) 
	return security_ops->kernel_create_files_as(new, inode);

}



int security_kernel_fw_from_file(struct file *file, char *buf, size_t size)

{

	return security_ops->kernel_fw_from_file(file, buf, size);

}

EXPORT_SYMBOL_GPL(security_kernel_fw_from_file);



int security_kernel_module_request(char *kmod_name)

{

	return security_ops->kernel_module_request(kmod_name);