ima: provide flag to identify new empty files

On ima_file_free(), newly created empty files are not labeled with
an initial security.ima value, because the iversion did not change.
Commit dff6efc "fs: fix iversion handling" introduced a change in
iversion behavior.  To verify this change use the shell command:

  $ (exec >foo)
  $ getfattr -h -e hex -d -m security foo

This patch defines the IMA_NEW_FILE flag.  The flag is initially
set, when IMA detects that a new file is created, and subsequently
checked on the ima_file_free() hook to set the initial security.ima
value.

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org>  3.14+

3 files changed, 13 insertions, 7 deletions

diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 86bfd5c5df85..a4605d677248 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -202,8 +202,11 @@ int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,
                         goto out;
 
                 cause = "missing-hash";
-                status =
-                    (inode->i_size == 0) ? INTEGRITY_PASS : INTEGRITY_NOLABEL;
+                status = INTEGRITY_NOLABEL;
+                if (inode->i_size == 0) {
+                        iint->flags |= IMA_NEW_FILE;
+                        status = INTEGRITY_PASS;
+                }
                 goto out;
         }
 
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 2917f980bf30..0a2298f90c9c 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -124,11 +124,13 @@ static void ima_check_last_writer(struct integrity_iint_cache *iint,
                 return;
 
         mutex_lock(&inode->i_mutex);
-        if (atomic_read(&inode->i_writecount) == 1 &&
-            iint->version != inode->i_version) {
-                iint->flags &= ~IMA_DONE_MASK;
-                if (iint->flags & IMA_APPRAISE)
-                        ima_update_xattr(iint, file);
+        if (atomic_read(&inode->i_writecount) == 1) {
+                if ((iint->version != inode->i_version) ||
+                    (iint->flags & IMA_NEW_FILE)) {
+                        iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE);
+                        if (iint->flags & IMA_APPRAISE)
+                                ima_update_xattr(iint, file);
+                }
         }
         mutex_unlock(&inode->i_mutex);
 }
diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 19b8e314ca96..904e68abd49e 100644
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -31,6 +31,7 @@
 #define IMA_DIGSIG              0x01000000
 #define IMA_DIGSIG_REQUIRED     0x02000000
 #define IMA_PERMIT_DIRECTIO     0x04000000
+#define IMA_NEW_FILE            0x08000000
 
 #define IMA_DO_MASK             (IMA_MEASURE | IMA_APPRAISE | IMA_AUDIT | \
                                  IMA_APPRAISE_SUBMASK)