[RFC PATCH 1/5] vfs: define a generic function to read a file from the kernel
Mimi Zohar
zohar at linux.vnet.ibm.com
Fri Jan 8 11:22:00 PST 2016
In order to measure and appraise files being read by the kernel,
new module and kexec syscalls were defined which include a file
descriptor. Other places in the kernel (eg. firmware, IMA,
sound) also read files.
This patch introduces a common function for reading files from
the kernel with the corresponding security post-read hook and
function.
Changelog:
- Add missing <linux/vmalloc.h>
Signed-off-by: Mimi Zohar <zohar at linux.vnet.ibm.com>
---
fs/exec.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 1 +
include/linux/lsm_hooks.h | 11 ++++++++++
include/linux/security.h | 9 ++++++++
security/security.c | 16 ++++++++++++++
5 files changed, 93 insertions(+)
diff --git a/fs/exec.c b/fs/exec.c
index b06623a..3c48a19 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -56,6 +56,7 @@
#include <linux/pipe_fs_i.h>
#include <linux/oom.h>
#include <linux/compat.h>
+#include <linux/vmalloc.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
@@ -831,6 +832,61 @@ int kernel_read(struct file *file, loff_t offset,
EXPORT_SYMBOL(kernel_read);
+int kernel_read_file(struct file *file, void **buf, loff_t *size,
+ loff_t max_size, int policy_id)
+{
+ loff_t i_size, pos;
+ ssize_t bytes = 0;
+ int ret;
+
+ if (!S_ISREG(file_inode(file)->i_mode))
+ return -EINVAL;
+
+ i_size = i_size_read(file_inode(file));
+ if (max_size > 0 && i_size > max_size)
+ return -EFBIG;
+ if (i_size == 0)
+ return -EINVAL;
+
+ *buf = vmalloc(i_size);
+ if (!*buf) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ pos = 0;
+ while (pos < i_size) {
+ bytes = kernel_read(file, pos, (char *)(*buf) + pos,
+ i_size - pos);
+ if (bytes < 0) {
+ ret = bytes;
+ goto out_free;
+ }
+
+ if (bytes == 0)
+ break;
+ pos += bytes;
+ }
+
+ if (pos != i_size) {
+ ret = -EBADF; /* firmware uses -EIO */
+ goto out_free;
+ }
+
+ ret = security_kernel_post_read_file(file, *buf, i_size, policy_id);
+ if (!ret)
+ *size = pos;
+
+out_free:
+ if (ret < 0) {
+ vfree(*buf);
+ *buf = NULL;
+ }
+out:
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kernel_read_file);
+
ssize_t read_code(struct file *file, unsigned long addr, loff_t pos, size_t len)
{
ssize_t res = vfs_read(file, (void __user *)addr, len, &pos);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3aa5142..9b1468c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2527,6 +2527,7 @@ static inline void i_readcount_inc(struct inode *inode)
extern int do_pipe_flags(int *, int);
extern int kernel_read(struct file *, loff_t, char *, unsigned long);
+extern int kernel_read_file(struct file *, void **, loff_t *, loff_t, int);
extern ssize_t kernel_write(struct file *, const char *, size_t, loff_t);
extern ssize_t __kernel_write(struct file *, const char *, size_t, loff_t *);
extern struct file * open_exec(const char *);
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 71969de..10baa8f 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -561,6 +561,14 @@
* 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.
+ * @kernel_post_read_file:
+ * Read a file specified by userspace.
+ * @file contains the file structure pointing to the file being read
+ * by the kernel.
+ * @buf pointer to buffer containing the file contents.
+ * @size length of the file contents.
+ * @policy_id contains the calling function identifier.
+ * 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
@@ -1457,6 +1465,8 @@ union security_list_options {
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,
+ int policy_id);
int (*task_fix_setuid)(struct cred *new, const struct cred *old,
int flags);
int (*task_setpgid)(struct task_struct *p, pid_t pgid);
@@ -1716,6 +1726,7 @@ struct security_hook_heads {
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;
struct list_head task_fix_setuid;
diff --git a/include/linux/security.h b/include/linux/security.h
index 4824a4c..44d8832 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -301,6 +301,8 @@ 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,
+ int policy_id);
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);
@@ -866,6 +868,13 @@ static inline int security_kernel_module_from_file(struct file *file)
return 0;
}
+static inline int security_kernel_post_read_file(struct file *file,
+ char *buf, loff_t size,
+ int policy_id)
+{
+ return 0;
+}
+
static inline int security_task_fix_setuid(struct cred *new,
const struct cred *old,
int flags)
diff --git a/security/security.c b/security/security.c
index e8ffd92..e979c2d 100644
--- a/security/security.c
+++ b/security/security.c
@@ -910,6 +910,20 @@ int security_kernel_module_from_file(struct file *file)
return ima_module_check(file);
}
+int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
+ int policy_id)
+{
+ int ret;
+
+ ret = call_int_hook(kernel_post_read_file, 0, file, buf, size,
+ policy_id);
+ if (ret)
+ return ret;
+
+ return ima_hash_and_process_file(file, buf, size, policy_id);
+}
+EXPORT_SYMBOL_GPL(security_kernel_post_read_file);
+
int security_task_fix_setuid(struct cred *new, const struct cred *old,
int flags)
{
@@ -1697,6 +1711,8 @@ struct security_hook_heads security_hook_heads = {
LIST_HEAD_INIT(security_hook_heads.kernel_module_request),
.kernel_module_from_file =
LIST_HEAD_INIT(security_hook_heads.kernel_module_from_file),
+ .kernel_post_read_file =
+ LIST_HEAD_INIT(security_hook_heads.kernel_post_read_file),
.task_fix_setuid =
LIST_HEAD_INIT(security_hook_heads.task_fix_setuid),
.task_setpgid = LIST_HEAD_INIT(security_hook_heads.task_setpgid),
--
2.1.0
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