linux-kernel - Re: suspicious rcu_dereference

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20101109090931.GH3971@swordfish.minsk.epam.com>
Date:	Tue, 9 Nov 2010 11:09:31 +0200
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, sergey.senozhatsky@...il.com
Subject: Re: suspicious rcu_dereference_check() usage splat

On (11/08/10 12:24), Paul E. McKenney wrote:
> Looking over the patch again, the scope of the RCU read-side critical
> section needs to expand to cover the use of the pointer as well as the
> call to find_task_by_vpid().  So, for example:
> 
> 		case IOPRIO_WHO_PROCESS:
> 			rcu_read_lock();
> 			if (!who)
> 				p = current;
> 			else
> 				p = find_task_by_vpid(who);
> 			if (p)
> 				ret = set_task_ioprio(p, ioprio);
> 			rcu_read_unlock();
> 			break;
> 		case IOPRIO_WHO_PGRP:
> 
> 
> Otherwise, the task could go away before the last use.
> 
> Sergey, could you please make this change and re-post your patch?
> 
> 							Thanx, Paul
> 

Hello,
Should we protect set_task_ioprio? Critical operations are protected
with rcu_read_lock/rcu_read_unlock in set_task_ioprio, the rest is protected
via task_lock(task)/task_unlock(task).

	Sergey

Content of type "application/pgp-signature" skipped