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authorKees Cook <keescook@chromium.org>2012-10-16 07:32:07 +1030
committerRusty Russell <rusty@rustcorp.com.au>2012-12-14 13:05:24 +1030
commit2e72d51b4ac32989496870cd8171b3682fea1839 (patch)
treeb8190d17aa5d59508f8c979ce0160f21bef89500
parent2f3238aebedb243804f58d62d57244edec4149b2 (diff)
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: Kees Cook <keescook@chromium.org> Acked-by: Serge E. Hallyn <serge.hallyn@canonical.com> Acked-by: Eric Paris <eparis@redhat.com> Acked-by: Mimi Zohar <zohar@us.ibm.com> Acked-by: James Morris <james.l.morris@oracle.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
-rw-r--r--include/linux/security.h13
-rw-r--r--kernel/module.c11
-rw-r--r--security/capability.c6
-rw-r--r--security/security.c5
4 files changed, 35 insertions, 0 deletions
diff --git a/include/linux/security.h b/include/linux/security.h
index 05e88bdcf7d9..0f6afc657f77 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -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)
diff --git a/kernel/module.c b/kernel/module.c
index 1395ca382fb5..a1d2ed8bab93 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -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;
diff --git a/security/capability.c b/security/capability.c
index b14a30c234b8..0fe5a026aef8 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -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);
diff --git a/security/security.c b/security/security.c
index 8dcd4ae10a5f..ce88630de15d 100644
--- a/security/security.c
+++ b/security/security.c
@@ -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)
{