IMA: update ima_counts_put

- As ima_counts_put() may be called after the inode has been freed,
verify that the inode is not NULL, before dereferencing it.

- Maintain the IMA file counters in may_open() properly, decrementing
any counter increments on subsequent errors.

Reported-by: Ciprian Docan <docan@eden.rutgers.edu>
Reported-by: J.R. Okajima <hooanon05@yahoo.co.jp>
Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Acked-by: Eric Paris <eparis@redhat.com
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 15 insertions, 7 deletions

diff --git a/fs/namei.c b/fs/namei.c
index f3c5b278895a..1f13751693a5 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1542,28 +1542,31 @@ int may_open(struct path *path, int acc_mode, int flag)
          * An append-only file must be opened in append mode for writing.
          */
         if (IS_APPEND(inode)) {
+                error = -EPERM;
                 if  ((flag & FMODE_WRITE) && !(flag & O_APPEND))
-                        return -EPERM;
+                        goto err_out;
                 if (flag & O_TRUNC)
-                        return -EPERM;
+                        goto err_out;
         }
 
         /* O_NOATIME can only be set by the owner or superuser */
         if (flag & O_NOATIME)
-                if (!is_owner_or_cap(inode))
-                        return -EPERM;
+                if (!is_owner_or_cap(inode)) {
+                        error = -EPERM;
+                        goto err_out;
+                }
 
         /*
          * Ensure there are no outstanding leases on the file.
          */
         error = break_lease(inode, flag);
         if (error)
-                return error;
+                goto err_out;
 
         if (flag & O_TRUNC) {
                 error = get_write_access(inode);
                 if (error)
-                        return error;
+                        goto err_out;
 
                 /*
                  * Refuse to truncate files with mandatory locks held on them.
@@ -1581,12 +1584,17 @@ int may_open(struct path *path, int acc_mode, int flag)
                 }
                 put_write_access(inode);
                 if (error)
-                        return error;
+                        goto err_out;
         } else
                 if (flag & FMODE_WRITE)
                         vfs_dq_init(inode);
 
         return 0;
+err_out:
+        ima_counts_put(path, acc_mode ?
+                       acc_mode & (MAY_READ | MAY_WRITE | MAY_EXEC) :
+                       ACC_MODE(flag) & (MAY_READ | MAY_WRITE));
+        return error;
 }
 
 /*