ima: audit log files opened with O_DIRECT flag

Files are measured or appraised based on the IMA policy.  When a
file, in policy, is opened with the O_DIRECT flag, a deadlock
occurs.

The first attempt at resolving this lockdep temporarily removed the
O_DIRECT flag and restored it, after calculating the hash.  The
second attempt introduced the O_DIRECT_HAVELOCK flag. Based on this
flag, do_blockdev_direct_IO() would skip taking the i_mutex a second
time.  The third attempt, by Dmitry Kasatkin, resolves the i_mutex
locking issue, by re-introducing the IMA mutex, but uncovered
another problem.  Reading a file with O_DIRECT flag set, writes
directly to userspace pages.  A second patch allocates a user-space
like memory.  This works for all IMA hooks, except ima_file_free(),
which is called on __fput() to recalculate the file hash.

Until this last issue is addressed, do not 'collect' the
measurement for measuring, appraising, or auditing files opened
with the O_DIRECT flag set.  Based on policy, permit or deny file
access.  This patch defines a new IMA policy rule option named
'permit_directio'.  Policy rules could be defined, based on LSM
or other criteria, to permit specific applications to open files
with the O_DIRECT flag set.

Changelog v1:
- permit or deny file access based IMA policy rules

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

1 files changed, 5 insertions, 1 deletions

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 93873a450ff7..40a7488f6721 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -353,7 +353,7 @@ enum {
         Opt_obj_user, Opt_obj_role, Opt_obj_type,
         Opt_subj_user, Opt_subj_role, Opt_subj_type,
         Opt_func, Opt_mask, Opt_fsmagic, Opt_uid, Opt_fowner,
-        Opt_appraise_type, Opt_fsuuid
+        Opt_appraise_type, Opt_fsuuid, Opt_permit_directio
 };
 
 static match_table_t policy_tokens = {
@@ -375,6 +375,7 @@ static match_table_t policy_tokens = {
         {Opt_uid, "uid=%s"},
         {Opt_fowner, "fowner=%s"},
         {Opt_appraise_type, "appraise_type=%s"},
+        {Opt_permit_directio, "permit_directio"},
         {Opt_err, NULL}
 };
 
@@ -622,6 +623,9 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
                         else
                                 result = -EINVAL;
                         break;
+                case Opt_permit_directio:
+                        entry->flags |= IMA_PERMIT_DIRECTIO;
+                        break;
                 case Opt_err:
                         ima_log_string(ab, "UNKNOWN", p);
                         result = -EINVAL;