Commit b44a7dfc authored by Mimi Zohar's avatar Mimi Zohar

vfs: define a generic function to read a file from the kernel

For a while it was looked down upon to directly read files from Linux.
These days there exists a few mechanisms in the kernel that do just
this though to load a file into a local buffer.  There are minor but
important checks differences on each.  This patch set is the first
attempt at resolving some of these differences.

This patch introduces a common function for reading files from the kernel
with the corresponding security post-read hook and function.

Changelog v4+:
- export security_kernel_post_read_file() - Fengguang Wu
v3:
- additional bounds checking - Luis
v2:
- To simplify patch review, re-ordered patches
Signed-off-by: default avatarMimi Zohar <zohar@linux.vnet.ibm.com>
Reviewed-by: default avatarLuis R. Rodriguez <mcgrof@suse.com>
Acked-by: default avatarKees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
parent 4b2530d8
......@@ -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 +832,58 @@ 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)
{
loff_t i_size, pos;
ssize_t bytes = 0;
int ret;
if (!S_ISREG(file_inode(file)->i_mode) || max_size < 0)
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)
return -ENOMEM;
pos = 0;
while (pos < i_size) {
bytes = kernel_read(file, pos, (char *)(*buf) + pos,
i_size - pos);
if (bytes < 0) {
ret = bytes;
goto out;
}
if (bytes == 0)
break;
pos += bytes;
}
if (pos != i_size) {
ret = -EIO;
goto out;
}
ret = security_kernel_post_read_file(file, *buf, i_size);
if (!ret)
*size = pos;
out:
if (ret < 0) {
vfree(*buf);
*buf = NULL;
}
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);
......
......@@ -2577,6 +2577,7 @@ 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);
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 *);
......
......@@ -561,6 +561,13 @@
* 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.
* 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 +1464,7 @@ 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 (*task_fix_setuid)(struct cred *new, const struct cred *old,
int flags);
int (*task_setpgid)(struct task_struct *p, pid_t pgid);
......@@ -1716,6 +1724,7 @@ 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;
......
......@@ -301,6 +301,7 @@ 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 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 +867,12 @@ 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)
{
return 0;
}
static inline int security_task_fix_setuid(struct cred *new,
const struct cred *old,
int flags)
......
......@@ -910,6 +910,12 @@ 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)
{
return call_int_hook(kernel_post_read_file, 0, file, buf, size);
}
EXPORT_SYMBOL_GPL(security_kernel_post_read_file);
int security_task_fix_setuid(struct cred *new, const struct cred *old,
int flags)
{
......@@ -1697,6 +1703,8 @@ 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),
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment