Re: task_for_pid never returns KERN_SUCCESS, any ideas?
Re: task_for_pid never returns KERN_SUCCESS, any ideas?
- Subject: Re: task_for_pid never returns KERN_SUCCESS, any ideas?
- From: Jason Coco <email@hidden>
- Date: Mon, 12 Jan 2009 13:45:36 -0500
On Jan 12, 2009, at 13:37 , Gary Fung wrote:
Jason Coco wrote:
On Jan 12, 2009, at 12:54 , Gary Fung wrote:
Tried to retrieve task_info_t by using task_for_pid but the
following code does not equate to true
task_t task = MACH_PORT_NULL;
struct task_basic_info tinf;
if(task_for_pid(mach_task_self(), pid, &task) == KERN_SUCCESS) {
... //not reached
}
mach_task_self returns non null value so that should be ok. But
task_for_pid does not return anything for &task. Any ideas? I've
iterated through all the pids currently running, same result. Ran it
on Leopard.
task_for_pid() requires special privileges to execute. Instead of
testing for KERN_SUCCESS in the future, I suggest using a variable to
test, then you can see exactly what failed (in this case, you will
not
have privileges to execute it).
The easiest way to deal with this (although, probably not the best
way) is to execute the application as root. You can see the man page
for taskgated(8) for more information on task_for_pid() and its
security issues.
Jason
It returns 5 for all pids, which is a KERN_FAILURE correct? This
doesn't provide much information at all. It only returns
KERN_SUCCESS for the running process itself. I thought you have
permission to retrieve task_info for other processes under the same
user?
No, it was deemed a security risk in one of the patches to tiger
(close to the release of leopard), and since that patch, you have to
have privileges to execute task_for_pid(), even for tasks owned by the
same user as the process. If the process is in the procmod or procview
group, it may be given access, or if it has the
system.privilege.taskport right, it will be given access. See
taskgated(8) for more information.
And yes, unfortunately 5 is just the general KERN_FAILURE, but it's
still good practice :)
Is there an easier way to retrieve the memory usage of a process?
Retrieving the pid and process name was not this difficult.
It is difficult because once you have the task port right, you can
inject anything into that task that you feel like. For instance, you
can start a new thread that the process knows nothing about and inject
it directly into the running process.
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