Commit 7928396d authored Apr 19, 2019 by Paul Moore Committed by Greg Kroah-Hartman May 25, 2019

proc: prevent changes to overridden credentials



commit 35a196bef449b5824033865b963ed9a43fb8c730 upstream.

Prevent userspace from changing the the /proc/PID/attr values if the
task's credentials are currently overriden.  This not only makes sense
conceptually, it also prevents some really bizarre error cases caused
when trying to commit credentials to a task with overridden
credentials.

Cc: <stable@vger.kernel.org>
Reported-by: "chengjian (D)" <cj.chengjian@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Acked-by: James Morris <james.morris@microsoft.com>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent bbd559ad

fs/proc/base.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -2542,6 +2542,11 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
		rcu_read_unlock();
		return -EACCES;
		}
		/* Prevent changes to overridden credentials. */
		if (current_cred() != current_real_cred()) {
		rcu_read_unlock();
		return -EBUSY;
		}
		rcu_read_unlock();

		if (count > PAGE_SIZE)