[RFC][PATCH] Prelim in-kernel filesystem auditing support

Hello, I know this one is a long time coming. My last patch was critically flawed in that the preallocation mechanism did not take into consideration multiple references to an inode holding audit info. This caused a complete melt down of the code. My first solution was a miserable failure. This one works much better. I went through 40 different tests just to make sure things are behaving [more] correctly. Two major scenarios that need to be thought over and most likely need a fixing are the following: 1. watch /etc/foo,filterkey=foo watch /etc/bar,filterkey=bar touch /etc/foo ln /etc/foo /etc/bar As of right now, /etc/bar will lose /etc/foo's watch information and gain /etc/bar's. This is the natural behavior for all other scenarios (ie: mv /etc/foo /etc/bar). I do not believe this should be allowed for hardlinks. The filterkey=bar may be a weaker filtering key then filterkey=foo and thus in any userspace filtering (we might decide to do) could be subverted. Hardlinks should retain, always, the filter information of what they're linking against, regardless of where they are at. This also brings into consideration the need for multiple watches on a single path? This way we get information for /etc/bar for both /etc/foo AND /etc/bar. 2. watch /etc/foo touch /etc/foo ln /etc/foo /tmp/foo (remains audited) mv /tmp/foo /tmp/bar (loses audit) This is also a natural side effect of the code. When we move we always lose any watch information we are holding onto. If we move into a location that's being watched we gain that watch information. Since /tmp/bar was not being watched, the hardlink loses its watch to /etc/foo. Is this acceptable? I don't think so. From my above statement, the hardlink must always retain it's watch information to what it is linked against.. We wouldn't want a user to be able to create a hardlink and then move it to lose the watch. But, we must also keep in mind that eventually it gets unreasonable. For instance: watch /etc/foo ln /etc/foo /etc/bar unwatch /etc/foo rm /etc/foo touch /etc/foo watch /etc/foo /etc/bar is no longer audited. There's no reasonable way around this. The data structure for this has become much more complex as I've incorporated the preallocation mechanism into the audit_watch structure itself with the assertion, "One chunk of audit_data memory per watch" -- This effectively introduces a circular data structure (the audit_data within the audit_wentry (at one time called audit_watch) is pointing at the audit_wentry itself. It'd take a long time to explain why, but I intend on releasing to this list, diagrams describing the data structure visually. I'll take a picture of my white board and post it for the time being. You might get a good laugh, I do. :) Please review and provide comments. PS: I did not use static inlines as Stephen suggested yet to keep the code consistent with what is already there. So keep me in check. I know I'm notorious for providing the wrong number of arguments to my macros! :( Patch #4: This patch will address the above issues in some way. It will finally take care of dynamic enable/disable of file system auditing from userspace. It will add permission masks filtering. Fix bugs found in Patch #3. Begin official Docbook comments. Figure out a good place to hook so we can cover unlinks and similar syscalls that skip over permission(). And anything else I'm presently forgetting :-) Hopefully by then I'll have some userspace code for the public. I originally wanted to remove some of Rik's code that hooked path_lookup(), but I actually kind of like it. Even though the inode he reports is wrong in some cases (ie: unlink()), the path information is useful. Especially when looking at hardlinks that are being watched. Might just take out the inode record. How does everyone feel about this? -- - Timothy R. Chavez