integrity: define a new function integrity_read_file()

This patch defines a new function called integrity_read_file()
to read file from the kernel into a buffer. Subsequent patches
will read a file containing the public keys and load them onto
the IMA keyring.

This patch moves and renames ima_kernel_read(), the non-security
checking version of kernel_read(), to integrity_kernel_read().

Changes in v3:
* Patch descriptions improved (Mimi)
* Add missing cast (kbuild test robot)

Changes in v2:
* configuration option removed
* function declared as '__init'

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

3 files changed, 85 insertions, 32 deletions

diff --git a/security/integrity/iint.c b/security/integrity/iint.c
index cc3eb4de18a1..dbee618526b6 100644
--- a/security/integrity/iint.c
+++ b/security/integrity/iint.c
@@ -19,6 +19,8 @@
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <linux/rbtree.h>
+#include <linux/file.h>
+#include <linux/uaccess.h>
 #include "integrity.h"
 
 static struct rb_root integrity_iint_tree = RB_ROOT;
@@ -167,3 +169,79 @@ static int __init integrity_iintcache_init(void)
         return 0;
 }
 security_initcall(integrity_iintcache_init);
+
+
+/*
+ * integrity_kernel_read - read data from the file
+ *
+ * This is a function for reading file content instead of kernel_read().
+ * It does not perform locking checks to ensure it cannot be blocked.
+ * It does not perform security checks because it is irrelevant for IMA.
+ *
+ */
+int integrity_kernel_read(struct file *file, loff_t offset,
+                          char *addr, unsigned long count)
+{
+        mm_segment_t old_fs;
+        char __user *buf = (char __user *)addr;
+        ssize_t ret = -EINVAL;
+
+        if (!(file->f_mode & FMODE_READ))
+                return -EBADF;
+
+        old_fs = get_fs();
+        set_fs(get_ds());
+        if (file->f_op->read)
+                ret = file->f_op->read(file, buf, count, &offset);
+        else if (file->f_op->aio_read)
+                ret = do_sync_read(file, buf, count, &offset);
+        else if (file->f_op->read_iter)
+                ret = new_sync_read(file, buf, count, &offset);
+        set_fs(old_fs);
+        return ret;
+}
+
+/*
+ * integrity_read_file - read entire file content into the buffer
+ *
+ * This is function opens a file, allocates the buffer of required
+ * size, read entire file content to the buffer and closes the file
+ *
+ * It is used only by init code.
+ *
+ */
+int __init integrity_read_file(const char *path, char **data)
+{
+        struct file *file;
+        loff_t size;
+        char *buf;
+        int rc = -EINVAL;
+
+        file = filp_open(path, O_RDONLY, 0);
+        if (IS_ERR(file)) {
+                rc = PTR_ERR(file);
+                pr_err("Unable to open file: %s (%d)", path, rc);
+                return rc;
+        }
+
+        size = i_size_read(file_inode(file));
+        if (size <= 0)
+                goto out;
+
+        buf = kmalloc(size, GFP_KERNEL);
+        if (!buf) {
+                rc = -ENOMEM;
+                goto out;
+        }
+
+        rc = integrity_kernel_read(file, 0, buf, size);
+        if (rc < 0)
+                kfree(buf);
+        else if (rc != size)
+                rc = -EIO;
+        else
+                *data = buf;
+out:
+        fput(file);
+        return rc;
+}
diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
index d34e7dfc1118..5df4d960d4dc 100644
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -67,36 +67,6 @@ MODULE_PARM_DESC(ahash_bufsize, "Maximum ahash buffer size");
 static struct crypto_shash *ima_shash_tfm;
 static struct crypto_ahash *ima_ahash_tfm;
 
-/**
- * ima_kernel_read - read file content
- *
- * This is a function for reading file content instead of kernel_read().
- * It does not perform locking checks to ensure it cannot be blocked.
- * It does not perform security checks because it is irrelevant for IMA.
- *
- */
-static int ima_kernel_read(struct file *file, loff_t offset,
-                           char *addr, unsigned long count)
-{
-        mm_segment_t old_fs;
-        char __user *buf = addr;
-        ssize_t ret = -EINVAL;
-
-        if (!(file->f_mode & FMODE_READ))
-                return -EBADF;
-
-        old_fs = get_fs();
-        set_fs(get_ds());
-        if (file->f_op->read)
-                ret = file->f_op->read(file, buf, count, &offset);
-        else if (file->f_op->aio_read)
-                ret = do_sync_read(file, buf, count, &offset);
-        else if (file->f_op->read_iter)
-                ret = new_sync_read(file, buf, count, &offset);
-        set_fs(old_fs);
-        return ret;
-}
-
 int __init ima_init_crypto(void)
 {
         long rc;
@@ -324,7 +294,8 @@ static int ima_calc_file_hash_atfm(struct file *file,
                 }
                 /* read buffer */
                 rbuf_len = min_t(loff_t, i_size - offset, rbuf_size[active]);
-                rc = ima_kernel_read(file, offset, rbuf[active], rbuf_len);
+                rc = integrity_kernel_read(file, offset, rbuf[active],
+                                           rbuf_len);
                 if (rc != rbuf_len)
                         goto out3;
 
@@ -417,7 +388,7 @@ static int ima_calc_file_hash_tfm(struct file *file,
         while (offset < i_size) {
                 int rbuf_len;
 
-                rbuf_len = ima_kernel_read(file, offset, rbuf, PAGE_SIZE);
+                rbuf_len = integrity_kernel_read(file, offset, rbuf, PAGE_SIZE);
                 if (rbuf_len < 0) {
                         rc = rbuf_len;
                         break;
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index f51ad65c894d..20d220481025 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -119,6 +119,10 @@ struct integrity_iint_cache {
  */
 struct integrity_iint_cache *integrity_iint_find(struct inode *inode);
 
+int integrity_kernel_read(struct file *file, loff_t offset,
+                          char *addr, unsigned long count);
+int __init integrity_read_file(const char *path, char **data);
+
 #define INTEGRITY_KEYRING_EVM           0
 #define INTEGRITY_KEYRING_MODULE        1
 #define INTEGRITY_KEYRING_IMA           2