Re: ptrace problem in 2.6.9

[Roland McGrath]

This is indeed a new bug, and it is not architecture-specific.  In my
recent changes to close some race conditions, I overlooked the case of a
process using PTRACE_ATTACH on its own children.  The new PT_ATTACHED flag
does not really mean "PTRACE_ATTACH was used", it means "PTRACE_ATTACH is
changing the ->parent link".  This patch fixes the problem that your test
program demonstrates.


Thanks,
Roland

Signed-off-by: Roland McGrath <roland@xxxxxxxxxx>

--- linux-2.6/kernel/ptrace.c 19 Oct 2004 06:12:06 -0000 1.38
+++ linux-2.6/kernel/ptrace.c 23 Oct 2004 04:43:20 -0000
@@ -132,7 +132,8 @@ int ptrace_attach(struct task_struct *ta
 		goto bad;
 
 	/* Go */
-	task->ptrace |= PT_PTRACED | PT_ATTACHED;
+	task->ptrace |= PT_PTRACED | ((task->real_parent != current)
+				      ? PT_ATTACHED : 0);
 	if (capable(CAP_SYS_PTRACE))
 		task->ptrace |= PT_PTRACE_CAP;
 	task_unlock(task);
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/