linux-kernel - RE: [PATCH RFC 4/4] 9p: fix race issue in fid contention.

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] [day] [month] [year] [list]

Message-ID: <HE1PR0802MB25555E46ABF8C53798B4FE5FF43F0@HE1PR0802MB2555.eurprd08.prod.outlook.com>
Date:   Fri, 18 Sep 2020 10:05:33 +0000
From:   Jianyong Wu <Jianyong.Wu@....com>
To:     Dominique Martinet <asmadeus@...ewreck.org>
CC:     "ericvh@...il.com" <ericvh@...il.com>,
        "lucho@...kov.net" <lucho@...kov.net>,
        "v9fs-developer@...ts.sourceforge.net" 
        <v9fs-developer@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Justin He <Justin.He@....com>, Greg Kurz <groug@...d.org>
Subject: RE: [PATCH RFC 4/4] 9p: fix race issue in fid contention.



> -----Original Message-----
> From: Dominique Martinet <asmadeus@...ewreck.org>
> Sent: Friday, September 18, 2020 5:35 PM
> To: Jianyong Wu <Jianyong.Wu@....com>
> Cc: ericvh@...il.com; lucho@...kov.net; v9fs-
> developer@...ts.sourceforge.net; linux-kernel@...r.kernel.org; Justin He
> <Justin.He@....com>; Greg Kurz <groug@...d.org>
> Subject: Re: [PATCH RFC 4/4] 9p: fix race issue in fid contention.
>
> Jianyong Wu wrote on Fri, Sep 18, 2020:
> > If we move the counter decrease code into p9_client_clunk and put it
> > instead of fid_atomic_dec, we need delete fid off the inode where it
> > stores in p9_client_clunk.
> > But there is no way can we acquire the inode in p9_client_clunk. Do
> > you have any idea? I think introduce another parameter for
> > p9_client_clunk Is not graceful.
>
> You cannot write code about the inode in p9_client_clunk, the way the code
> is split fs/9p can refer to net/9p but not the other way around (module-wise,
> 9p can refer to 9pnet but 9pnet cannot refer to 9p or we would have cyclic
> dependencies)
>
> However I don't see what bothers you.
> v9fs_dir_release can remove the fid from the inode as it does currently and
> just clunk immediately afterwards.
>
>
> If another user of the fid had gotten the fid from the inode previously, it has
> a ref, so the fid will not be actually clunked then but it will be clunked later
> when it is done being used -- that is perfectly fine ?
>
> p9_client_clunk should not have to worry about anything in the vfs.
>
Yeah, I see. That's it.

Thanks
Jianyong
> --
> Dominique
IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.