CRED: Guard the setprocattr security hook against ptrace
Guard the setprocattr security hook against ptrace by taking the target task's
cred_guard_mutex around it. The problem is that setprocattr() may otherwise
note the lack of a debugger, and then perform an action on that basis whilst
letting a debugger attach between the two points. Holding cred_guard_mutex
across the test and the action prevents ptrace_attach() from doing that.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/fs/proc/base.c b/fs/proc/base.c
index fb45615..23342e1 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2128,9 +2128,15 @@
if (copy_from_user(page, buf, count))
goto out_free;
+ /* Guard against adverse ptrace interaction */
+ length = mutex_lock_interruptible(&task->cred_guard_mutex);
+ if (length < 0)
+ goto out_free;
+
length = security_setprocattr(task,
(char*)file->f_path.dentry->d_name.name,
(void*)page, count);
+ mutex_unlock(&task->cred_guard_mutex);
out_free:
free_page((unsigned long) page);
out: