Re: [PATCH 4/4] Swap migration V3: sys_migrate_pages interface

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

On Fri, 21 Oct 2005, Ray Bryant wrote:

> That code used to be there.    Basically the check was that if you could 
> legally send a signal to the process, you could migrate its memory.
> Go back and look and my patches for this.
> 
> Why was this dropped, arbitrarily?

Sorry, it was separated out from the sys_migrate patch.

Here is the fix:

Index: linux-2.6.14-rc4-mm1/mm/mempolicy.c
===================================================================
--- linux-2.6.14-rc4-mm1.orig/mm/mempolicy.c	2005-10-20 14:45:45.000000000 -0700
+++ linux-2.6.14-rc4-mm1/mm/mempolicy.c	2005-10-21 09:32:19.000000000 -0700
@@ -784,12 +784,26 @@ asmlinkage long sys_migrate_pages(pid_t 
 	if (!mm)
 		return -EINVAL;
 
+	/*
+	 * Permissions check like for signals.
+	 * See check_kill_permission()
+	 */
+	if ((current->euid ^ task->suid) && (current->euid ^ task->uid) &&
+	    (current->uid ^ task->suid) && (current->uid ^ task->uid) &&
+	    !capable(CAP_SYS_ADMIN)) {
+		err = -EPERM;
+		goto out;
+	}
+
 	/* Is the user allowed to access the target nodes? */
-	if (!nodes_subset(new, cpuset_mems_allowed(task)))
-		return -EPERM;
+	if (!nodes_subset(new, cpuset_mems_allowed(task)) &&
+	    !capable(CAP_SYS_ADMIN)) {
+		err= -EPERM;
+		goto out;
+	}
 
 	err = do_migrate_pages(mm, &old, &new, MPOL_MF_MOVE);
-
+out:
 	mmput(mm);
 	return err;
 }

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