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authorMimi Zohar <zohar@linux.vnet.ibm.com>2015-12-28 16:02:29 -0500
committerMimi Zohar <zohar@linux.vnet.ibm.com>2016-02-18 17:14:03 -0500
commitb44a7dfc6fa16e01f2497c9fa62c3926f94be174 (patch)
treeb48ced5b7c84986778ca4ac3b6bf3f13c74f2ef2
parent4b2530d819e179ae3352c38a1ceff929a922d070 (diff)
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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: Mimi Zohar <zohar@linux.vnet.ibm.com> Reviewed-by: Luis R. Rodriguez <mcgrof@suse.com> Acked-by: Kees Cook <keescook@chromium.org> Cc: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/exec.c53
-rw-r--r--include/linux/fs.h1
-rw-r--r--include/linux/lsm_hooks.h9
-rw-r--r--include/linux/security.h7
-rw-r--r--security/security.c8
5 files changed, 78 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c
index dcd4ac7d3f1e..6b6668baa44a 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 +832,58 @@ 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);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ae681002100a..9a83d82b61ac 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -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 *);
diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
index 71969de4058c..f82631cc7248 100644
--- a/include/linux/lsm_hooks.h
+++ b/include/linux/lsm_hooks.h
@@ -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;
diff --git a/include/linux/security.h b/include/linux/security.h
index 4824a4ccaf1c..f30f5647d1e1 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -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)
diff --git a/security/security.c b/security/security.c
index e8ffd92ae2eb..c98dd6bf4ebd 100644
--- a/security/security.c
+++ b/security/security.c
@@ -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),