Re: [PATCH ghak90 V8 13/16] audit: track container nesting

On 2020-02-13 16:49, Paul Moore wrote: > On Wed, Feb 5, 2020 at 6:51 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > On 2020-02-05 18:05, Paul Moore wrote: > > > On Thu, Jan 30, 2020 at 2:28 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > > > On 2020-01-22 16:29, Paul Moore wrote: > > > > > On Tue, Dec 31, 2019 at 2:51 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > > > > > > > > > > > Track the parent container of a container to be able to filter and > > > > > > report nesting. > > > > > > > > > > > > Now that we have a way to track and check the parent container of a > > > > > > container, modify the contid field format to be able to report that > > > > > > nesting using a carrat ("^") separator to indicate nesting. The > > > > > > original field format was "contid=<contid>" for task-associated records > > > > > > and "contid=<contid>[,<contid>[...]]" for network-namespace-associated > > > > > > records. The new field format is > > > > > > "contid=<contid>[^<contid>[...]][,<contid>[...]]". > > > > > > > > > > Let's make sure we always use a comma as a separator, even when > > > > > recording the parent information, for example: > > > > > "contid=<contid>[,^<contid>[...]][,<contid>[...]]" > > > > > > > > The intent here is to clearly indicate and separate nesting from > > > > parallel use of several containers by one netns. If we do away with > > > > that distinction, then we lose that inheritance accountability and > > > > should really run the list through a "uniq" function to remove the > > > > produced redundancies. This clear inheritance is something Steve was > > > > looking for since tracking down individual events/records to show that > > > > inheritance was not aways feasible due to rolled logs or search effort. > > > > > > Perhaps my example wasn't clear. I'm not opposed to the little > > > carat/hat character indicating a container's parent, I just think it > > > would be good to also include a comma *in*addition* to the carat/hat. > > > > Ah, ok. Well, I'd offer that it would be slightly shorter, slightly > > less cluttered and having already written the parser in userspace, I > > think the parser would be slightly simpler. > > > > I must admit, I was a bit puzzled by your snippet of code that was used > > as a prefix to the next item rather than as a postfix to the given item. > > > > Can you say why you prefer the comma in addition? > > Generally speaking, I believe that a single delimiter is both easier > for the eyes to parse, and easier/safer for machines to parse as well. > In this particular case I think of the comma as a delimiter and the > carat as a modifier, reusing the carat as a delimiter seems like a bad > idea to me. I'm not crazy about this idea, but I'll have a look at how much work it is to recode the userspace search tools. It also adds extra characters and noise into the string format that seems counterproductive.

> > > > > > diff --git a/kernel/audit.c b/kernel/audit.c > > > > > > index ef8e07524c46..68be59d1a89b 100644 > > > > > > --- a/kernel/audit.c > > > > > > +++ b/kernel/audit.c > > > > > > > > > > > @@ -492,6 +493,7 @@ void audit_switch_task_namespaces(struct nsproxy *ns, struct task_struct *p) > > > > > > audit_netns_contid_add(new->net_ns, contid); > > > > > > } > > > > > > > > > > > > +void audit_log_contid(struct audit_buffer *ab, u64 contid); > > > > > > > > > > If we need a forward declaration, might as well just move it up near > > > > > the top of the file with the rest of the declarations. > > > > > > > > Ok. > > > > > > > > > > +void audit_log_contid(struct audit_buffer *ab, u64 contid) > > > > > > +{ > > > > > > + struct audit_contobj *cont = NULL, *prcont = NULL; > > > > > > + int h; > > > > > > > > > > It seems safer to pass the audit container ID object and not the u64. > > > > > > > > It would also be faster, but in some places it isn't available such as > > > > for ptrace and signal targets. This also links back to the drop record > > > > refcounts to hold onto the contobj until process exit, or signal > > > > delivery. > > > > > > > > What we could do is to supply two potential parameters, a contobj and/or > > > > a contid, and have it use the contobj if it is valid, otherwise, use the > > > > contid, as is done for names and paths supplied to audit_log_name(). > > > > > > Let's not do multiple parameters, that begs for misuse, let's take the > > > wrapper function route: > > > > > > func a(int id) { > > > // important stuff > > > } > > > > > > func ao(struct obj) { > > > a(obj.id); > > > } > > > > > > ... and we can add a comment that you *really* should be using the > > > variant that passes an object. > > > > I was already doing that where it available, and dereferencing the id > > for the call. But I see an advantage to having both parameters supplied > > to the function, since it saves us the trouble of dereferencing it, > > searching for the id in the hash list and re-locating the object if the > > object is already available. > > I strongly prefer we not do multiple parameters for the same "thing"; So do I, ideally. However... > I would much rather do the wrapper approach as described above. I > would also like to see us use the audit container ID object as much as > possible, using a bare integer should be a last resort. It is not clear to me that you understood what I wrote above. I can't use the object pointer where preferable because there are a few cases where only the ID is available. If only the ID is available, I would have to make a best effort to look up the object pointer and am not guaranteed to find it (invalid, stale, signal info...). If I am forced to use only one, it becomes the ID that is used, and I no longer have the benefit of already having the object pointer for certainty and saving work. For all cases where I have the object pointer, which is most cases, and most frequently used cases, I will have to dereference the object pointer to an ID, then go through the work again to re-locate the object pointer. This is less certain, and more work. Reluctantly, the only practical solution I see here is to supply both, favouring the object pointer if it is valid, then falling back on the ID from the next parameter.