| 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
| ||
|
Date: Sun, 13 Nov 2016 20:43:12 +0200
From: Amir Goldstein <amir73il@...il.com>
To: Jan Kara <jack@...e.cz>
Cc: Miklos Szeredi <miklos@...redi.hu>, Eric Paris <eparis@...hat.com>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: fsnotify_mark_srcu wtf?
On Thu, Nov 10, 2016 at 9:46 PM, Jan Kara <jack@...e.cz> wrote:
...
>
> Well but how would you like to protect the mark list hanging off the inode
> / mountpoint with two SRCUs? You'd need two lists hanging off the inode &
> mountpoint (for different priorities) and that's too big cost to pay to
> accomodate broken userspace...
>
This is the plan.
I have a rough implementation, which still requires some testing:
/*
* fsnotify_perm_mark[1] protects reads of the first half of inode/vfsmount
* mark lists, which consist of the high priority (>0) marks, whose masks
* may contain permission events.
*
* fsnotify_perm_mark[0] protects reads of the second half of inode/vfsmount
* mark lists, which consist of the low priority (0) marks, whose masks
* do not contain permission events.
*
* High priority marks and low priority marks are added to different
* destroy lists and freed by different reapers, who synchronize only
* the relevant srcu.
*
* Before traversing to first mark on the list we must hold both srcu.
* While traversing first half, we may temporary drop fsnotify_perm_mark[0]
* to handle a blocking permission event.
* When we reach the first low level mark, we may drop fsnotify_perm_mark[1]
* for good.
*/
Powered by blists - more mailing lists