path: root/security/integrity/ima/ima.h
diff options
authorEric Paris <eparis@redhat.com>2010-10-25 14:41:52 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-26 11:37:18 -0700
commitb9593d309d17c57e9ddc3934d641902533896ca9 (patch)
treefa7fd9ced4a79f102e653ee4a5dc348aa1a41c21 /security/integrity/ima/ima.h
parentad16ad00c34d3f320a5876b3d711ef6bc81362e1 (diff)
IMA: use i_writecount rather than a private counter
IMA tracks the number of struct files which are holding a given inode readonly and the number which are holding the inode write or r/w. It needs this information so when a new reader or writer comes in it can tell if this new file will be able to invalidate results it already made about existing files. aka if a task is holding a struct file open RO, IMA measured the file and recorded those measurements and then a task opens the file RW IMA needs to note in the logs that the old measurement may not be correct. It's called a "Time of Measure Time of Use" (ToMToU) issue. The same is true is a RO file is opened to an inode which has an open writer. We cannot, with any validity, measure the file in question since it could be changing. This patch attempts to use the i_writecount field to track writers. The i_writecount field actually embeds more information in it's value than IMA needs but it should work for our purposes and allow us to shrink the struct inode even more. Signed-off-by: Eric Paris <eparis@redhat.com> Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'security/integrity/ima/ima.h')
1 files changed, 0 insertions, 1 deletions
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 80aca3d2cb7..b546b90f5fa 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -108,7 +108,6 @@ struct ima_iint_cache {
struct mutex mutex; /* protects: version, flags, digest */
/* protected by inode->i_lock */
unsigned int readcount; /* measured files readcount */
- unsigned int writecount;/* measured files writecount */
struct kref refcount; /* ima_iint_cache reference count */