1 files changed, 28 insertions, 13 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 8dcb8f6..019e04e 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -118,6 +118,33 @@ int ptrace_check_attach(struct task_struct *child, int kill)
 	return ret;
 }
 
+static int may_attach(struct task_struct *task)
+{
+	if (!task->mm)
+		return -EPERM;
+	if (((current->uid != task->euid) ||
+	     (current->uid != task->suid) ||
+	     (current->uid != task->uid) ||
+	     (current->gid != task->egid) ||
+	     (current->gid != task->sgid) ||
+	     (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
+		return -EPERM;
+	smp_rmb();
+	if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
+		return -EPERM;
+
+	return security_ptrace(current, task);
+}
+
+int ptrace_may_attach(struct task_struct *task)
+{
+	int err;
+	task_lock(task);
+	err = may_attach(task);
+	task_unlock(task);
+	return !err;
+}
+
 int ptrace_attach(struct task_struct *task)
 {
 	int retval;
@@ -127,22 +154,10 @@ int ptrace_attach(struct task_struct *task)
 		goto bad;
 	if (task == current)
 		goto bad;
-	if (!task->mm)
-		goto bad;
-	if(((current->uid != task->euid) ||
-	    (current->uid != task->suid) ||
-	    (current->uid != task->uid) ||
- 	    (current->gid != task->egid) ||
- 	    (current->gid != task->sgid) ||
- 	    (current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
-		goto bad;
-	smp_rmb();
-	if (!task->mm->dumpable && !capable(CAP_SYS_PTRACE))
-		goto bad;
 	/* the same process cannot be attached many times */
 	if (task->ptrace & PT_PTRACED)
 		goto bad;
-	retval = security_ptrace(current, task);
+	retval = may_attach(task);
 	if (retval)
 		goto bad;