ima: skip memory allocation for empty files

Memory allocation is unnecessary for empty files.
This patch calculates the hash without memory allocation.

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

1 files changed, 12 insertions, 8 deletions

diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
index d257e3631152..1bde8e627766 100644
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -87,16 +87,20 @@ static int ima_calc_file_hash_tfm(struct file *file,
         if (rc != 0)
                 return rc;
 
-        rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
-        if (!rbuf) {
-                rc = -ENOMEM;
+        i_size = i_size_read(file_inode(file));
+
+        if (i_size == 0)
                 goto out;
-        }
+
+        rbuf = kzalloc(PAGE_SIZE, GFP_KERNEL);
+        if (!rbuf)
+                return -ENOMEM;
+
         if (!(file->f_mode & FMODE_READ)) {
                 file->f_mode |= FMODE_READ;
                 read = 1;
         }
-        i_size = i_size_read(file_inode(file));
+
         while (offset < i_size) {
                 int rbuf_len;
 
@@ -113,12 +117,12 @@ static int ima_calc_file_hash_tfm(struct file *file,
                 if (rc)
                         break;
         }
-        kfree(rbuf);
-        if (!rc)
-                rc = crypto_shash_final(&desc.shash, hash->digest);
         if (read)
                 file->f_mode &= ~FMODE_READ;
+        kfree(rbuf);
 out:
+        if (!rc)
+                rc = crypto_shash_final(&desc.shash, hash->digest);
         return rc;
 }