On Wed, Apr 17, 2019 at 12:27 PM Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
On 04/17, Paul Moore wrote:True, or at least I would think so.
On Wed, Apr 17, 2019 at 10:57 AM Oleg Nesterov <oleg@xxxxxxxxxx> wrote:Yes, but if proc_pid_attr_write() is called with cred != real_cred then
On 04/17, Paul Moore wrote:Yes, that is simple, but I worry about what other LSMs might want to
I'm tempted to simply return an error in selinux_setprocattr() ifWhat about other modules? I have no idea what smack_setprocattr() is,
the task's credentials are not the same as its real_cred;
but it too does prepare_creds/commit creds.
it seems that the simplest workaround should simply add the additional
cred == real_cred into proc_pid_attr_write().
do. While I believe failing if the effective creds are not the same
as the real_creds is okay for SELinux (possibly Smack too), I worry
about what other LSMs may want to do. After all,
proc_pid_attr_write() doesn't change the the creds itself, that is
something the specific LSMs do.
something is already wrong?
Looking at the current tree there are three LSMs which implement
setprocattr hooks: SELinux, Smack, and AppArmor. I know Casey has
already mentioned that he wasn't able to trigger the problem in Smack,
but looking at smack_setprocattr() I see the similar commit_creds()
usage so I would expect the same problem in Smack; what say you Casey?
Looking at apparmor_setprocattr(), it appears that it too could end
up calling commit_creds() via aa_set_current_hat().
Since it looks like all three LSMs which implement the setprocattr
hook are vulnerable I'm open to the idea that proc_pid_attr_write() is
a better choice for the cred != read_cred check, but I would want to
make sure John and Casey are okay with that.