Re: [PATCH 5/5] Swap Migration V5: sys_migrate_pages interface

[Christoph Lameter <clameter@engr.sgi.com>]

On Mon, 31 Oct 2005, Andrew Morton wrote:

> Christoph Lameter <clameter@sgi.com> wrote:
> > +	 * Permissions check like for signals.
> > +	 * See check_kill_permission()
> Obscure.  Can you please explain the thinking behind putting this check in
> here?  Preferably via a comment...
> 

Index: linux-2.6.14-rc5-mm1/mm/mempolicy.c
===================================================================
--- linux-2.6.14-rc5-mm1.orig/mm/mempolicy.c	2005-11-01 09:32:46.000000000 -0800
+++ linux-2.6.14-rc5-mm1/mm/mempolicy.c	2005-11-01 09:38:46.000000000 -0800
@@ -790,8 +790,15 @@ asmlinkage long sys_migrate_pages(pid_t 
 		return -EINVAL;
 
 	/*
-	 * Permissions check like for signals.
-	 * See check_kill_permission()
+	 * We only allow a process to move the pages of another
+	 * if the process issuing sys_migrate has the right to send a kill
+	 * signal to the process to be moved. Moving another processes
+	 * memory may impact the performance of that process. If the
+	 * process issuing sys_migrate_pages has the right to kill the
+	 * target process then obviously that process has the right to
+	 * impact the performance of the target process.
+	 *
+	 * The permission check was taken from  check_kill_permission()
 	 */
 	if ((current->euid ^ task->suid) && (current->euid ^ task->uid) &&
 	    (current->uid ^ task->suid) && (current->uid ^ task->uid) &&
-
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