linux-kernel - Re: module: fix module_refcount() return when running in a module exit routine

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: <20150123131758.GC8045@infradead.org>
Date:	Fri, 23 Jan 2015 05:17:58 -0800
From:	Christoph Hellwig <hch@...radead.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: module: fix module_refcount() return when running in a module
 exit routine

On Fri, Jan 23, 2015 at 01:24:15PM +1030, Rusty Russell wrote:
> The correct fix is to turn try_module_get() into __module_get(), and
> always do the module_put().

Is this really safe?  __module_get sais it needs a non-zero refcount
to start with, but scsi_device_get is the only thing every incrementing
the refcount on the module pointer in the scsi host template, so
exactly that case can happen easily.  There's not assert actually
hardcoding the assumption, so I'm not sure if requirement the comment
really just is nice to have or a strong requirement.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/