[PATCH v2 0/2] ima: minimize open-writers and ToMToU violations

[Mimi Zohar <zohar@linux.ibm.com>]

Each time a file in policy, that is already opened for write, is opened
for read, an open-writers integrity violation audit message is emitted
and a violation record is added to the IMA measurement list.

Similarly each time a file in policy, that is already opened for read,
is opened for write, a Time-of-Measure-Time-of-Use (ToMToU) integrity
violation audit message is emitted and a violation record is added to
the IMA measurement list.

As there is no benefit in having multiple open-writers or ToMToU
violations for the same file open in the audit log and IMA measurement
list, minimize them.

Minimizing open-writer violations results in a single open-writers
violation being emitted until all writers are closed no matter the
number of subsequent file open readers (or writers).

Minimizing ToMToU violations results in a single ToMToU violation being
emitted for all subsequent file open writers, until another in policy
file open reader.

Since the IMA_MUST_MEASURE atomic flag is only used for tracking ToMToU
violations, rename the atomic flag to IMA_MAY_EMIT_TOMTOU.

Define a new atomic flag named IMA_EMITTED_OPENWRITERS to minimize
open-writer violations.

Mimi Zohar (2):
  ima: limit the number of open-writers integrity violations
  ima: limit the number of ToMToU integrity violations

 security/integrity/ima/ima.h      |  3 ++-
 security/integrity/ima/ima_main.c | 18 +++++++++++++-----
 2 files changed, 15 insertions(+), 6 deletions(-)

--
2.48.1