ima: forbid write access to files with digital signatures

This patch forbids write access to files with digital signatures, as they
are considered immutable.

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

1 files changed, 5 insertions, 2 deletions

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index d743c9a0a4b4..cd00ba39e8e0 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -175,12 +175,12 @@ static int process_measurement(struct file *file, const char *filename,
         if (!action) {
                 if (iint->flags & IMA_APPRAISED)
                         rc = iint->ima_status;
-                goto out;
+                goto out_digsig;
         }
 
         rc = ima_collect_measurement(iint, file);
         if (rc != 0)
-                goto out;
+                goto out_digsig;
 
         if (function != BPRM_CHECK)
                 pathname = ima_d_path(&file->f_path, &pathbuf);
@@ -195,6 +195,9 @@ static int process_measurement(struct file *file, const char *filename,
         if (action & IMA_AUDIT)
                 ima_audit_measurement(iint, pathname);
         kfree(pathbuf);
+out_digsig:
+        if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG))
+                rc = -EACCES;
 out:
         mutex_unlock(&inode->i_mutex);
         if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE))