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Commit 2e72d51b authored by Kees Cook's avatar Kees Cook Committed by Rusty Russell
Browse files

security: introduce kernel_module_from_file hook 



Now that kernel module origins can be reasoned about, provide a hook to
the LSMs to make policy decisions about the module file. This will let
Chrome OS enforce that loadable kernel modules can only come from its
read-only hash-verified root filesystem. Other LSMs can, for example,
read extended attributes for signatures, etc.

Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Acked-by: default avatarSerge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: default avatarEric Paris <eparis@redhat.com>
Acked-by: default avatarMimi Zohar <zohar@us.ibm.com>
Acked-by: default avatarJames Morris <james.l.morris@oracle.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 2f3238ae

include/linux/security.h

+13 −0
Original line number Diff line number Diff line
@@ -694,6 +694,12 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts) 
 *	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_module_from_file:

 *	Load a kernel module from userspace.

 *	@file contains the file structure pointing to the file containing

 *	the kernel module to load. If the module is being loaded from a blob,

 *	this argument will be NULL.

 *	Return 0 if permission is granted.

 * @task_fix_setuid:

 *	Update the module's state after setting one or more of the user

 *	identity attributes of the current process.  The @flags parameter
@@ -1508,6 +1514,7 @@ struct security_operations { 
	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_module_from_file)(struct file *file);

	int (*task_fix_setuid) (struct cred *new, const struct cred *old,

				int flags);

	int (*task_setpgid) (struct task_struct *p, pid_t pgid);
@@ -1765,6 +1772,7 @@ 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_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,

			     int flags);

int security_task_setpgid(struct task_struct *p, pid_t pgid);
@@ -2278,6 +2286,11 @@ static inline int security_kernel_module_request(char *kmod_name) 
	return 0;

}



static inline int security_kernel_module_from_file(struct file *file)

{

	return 0;

}



static inline int security_task_fix_setuid(struct cred *new,

					   const struct cred *old,

					   int flags)

kernel/module.c

+11 −0
Original line number Diff line number Diff line
@@ -29,6 +29,7 @@ 
#include <linux/vmalloc.h>

#include <linux/elf.h>

#include <linux/proc_fs.h>

#include <linux/security.h>

#include <linux/seq_file.h>

#include <linux/syscalls.h>

#include <linux/fcntl.h>
@@ -2485,10 +2486,16 @@ static int elf_header_check(struct load_info *info) 
static int copy_module_from_user(const void __user *umod, unsigned long len,

				  struct load_info *info)

{

	int err;



	info->len = len;

	if (info->len < sizeof(*(info->hdr)))

		return -ENOEXEC;



	err = security_kernel_module_from_file(NULL);

	if (err)

		return err;



	/* Suck in entire file: we'll want most of it. */

	info->hdr = vmalloc(info->len);

	if (!info->hdr)
@@ -2515,6 +2522,10 @@ static int copy_module_from_fd(int fd, struct load_info *info) 
	if (!file)

		return -ENOEXEC;



	err = security_kernel_module_from_file(file);

	if (err)

		goto out;



	err = vfs_getattr(file->f_vfsmnt, file->f_dentry, &stat);

	if (err)

		goto out;

security/capability.c

+6 −0
Original line number Diff line number Diff line
@@ -395,6 +395,11 @@ static int cap_kernel_module_request(char *kmod_name) 
	return 0;

}



static int cap_kernel_module_from_file(struct file *file)

{

	return 0;

}



static int cap_task_setpgid(struct task_struct *p, pid_t pgid)

{

	return 0;
@@ -967,6 +972,7 @@ void __init security_fixup_ops(struct security_operations *ops) 
	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_module_request);

	set_to_cap_if_null(ops, kernel_module_from_file);

	set_to_cap_if_null(ops, task_fix_setuid);

	set_to_cap_if_null(ops, task_setpgid);

	set_to_cap_if_null(ops, task_getpgid);

security/security.c

+5 −0
Original line number Diff line number Diff line
@@ -820,6 +820,11 @@ int security_kernel_module_request(char *kmod_name) 
	return security_ops->kernel_module_request(kmod_name);

}



int security_kernel_module_from_file(struct file *file)

{

	return security_ops->kernel_module_from_file(file);

}



int security_task_fix_setuid(struct cred *new, const struct cred *old,

			     int flags)

{