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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>
hifive-unleashed-5.1
David Howells 2009-05-08 13:55:27 +01:00 committed by James Morris
parent 5e751e992f
commit 107db7c7dd
1 changed files with 6 additions and 0 deletions
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6
fs/proc/base.c
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@ -2128,9 +2128,15 @@ static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
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: