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>
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