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From: Greg KH <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>
To: Benjamin Herrenschmidt
	<benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
Cc: Cyril Bur <cyrilbur-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	jassisinghbrar-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	arnd-r2nGTMty4D4@public.gmane.org,
	joel-U3u1mxZcP9KHXe+LvDLADg@public.gmane.org,
	mark.rutland-5wv7dgnIgG8@public.gmane.org,
	robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	openbmc-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org,
	andrew-zrmu5oMJ5Fs@public.gmane.org,
	xow-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org,
	jk-mnsaURCQ41sdnm+yROfE0A@public.gmane.org
Subject: Re: [PATCH 3/4] drivers/misc: Add ASpeed LPC control driver
Date: Thu, 12 Jan 2017 17:26:19 +0100	[thread overview]
Message-ID: <20170112162619.GB10283@kroah.com> (raw)
In-Reply-To: <1484237253.2492.43.camel-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>

On Thu, Jan 12, 2017 at 10:07:33AM -0600, Benjamin Herrenschmidt wrote:
> On Thu, 2017-01-12 at 17:00 +0100, Greg KH wrote:
> > > How so ? I mean, access_ok followed by __get/__put_user is still a
> > > classic, what's wrong with it ?
> > 
> > No "normal" driver should do that, just call copy_to/from_user and be
> > done with it.  That way all of the proper locking and validation checks
> > like this are done correctly for you.  Why would a driver ever call the
> > "raw" __get/__put_user functions?
> 
> I supposed historically it was considered faster for some things :-)
> 
> Not a huge deal, and yes it's probably cleaner, I was just wondering
> what was "racy" about access_ok() that I might have missed...

I think, you can change things after access_ok() happens, there used to
be bugs in that area a few years ago.  I think we fixed them by moving
the offending drivers to use copy_*() instead.

thanks,

greg k-h
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WARNING: multiple messages have this Message-ID (diff)
From: Greg KH <gregkh@linuxfoundation.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Cyril Bur <cyrilbur@gmail.com>,
	devicetree@vger.kernel.org, jassisinghbrar@gmail.com,
	arnd@arndb.de, joel@jms.id.au, mark.rutland@arm.com,
	robh+dt@kernel.org, openbmc@lists.ozlabs.org, andrew@aj.id.au,
	xow@google.com, jk@ozlabs.org
Subject: Re: [PATCH 3/4] drivers/misc: Add ASpeed LPC control driver
Date: Thu, 12 Jan 2017 17:26:19 +0100	[thread overview]
Message-ID: <20170112162619.GB10283@kroah.com> (raw)
In-Reply-To: <1484237253.2492.43.camel@kernel.crashing.org>

On Thu, Jan 12, 2017 at 10:07:33AM -0600, Benjamin Herrenschmidt wrote:
> On Thu, 2017-01-12 at 17:00 +0100, Greg KH wrote:
> > > How so ? I mean, access_ok followed by __get/__put_user is still a
> > > classic, what's wrong with it ?
> > 
> > No "normal" driver should do that, just call copy_to/from_user and be
> > done with it.  That way all of the proper locking and validation checks
> > like this are done correctly for you.  Why would a driver ever call the
> > "raw" __get/__put_user functions?
> 
> I supposed historically it was considered faster for some things :-)
> 
> Not a huge deal, and yes it's probably cleaner, I was just wondering
> what was "racy" about access_ok() that I might have missed...

I think, you can change things after access_ok() happens, there used to
be bugs in that area a few years ago.  I think we fixed them by moving
the offending drivers to use copy_*() instead.

thanks,

greg k-h

  parent reply	other threads:[~2017-01-12 16:26 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-12  0:29 [PATCH 0/4] ASpeed mailbox and LPC control drivers Cyril Bur
2017-01-12  0:29 ` Cyril Bur
     [not found] ` <20170112002910.3650-1-cyrilbur-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-01-12  0:29   ` [PATCH 1/4] Documentation: dt: mailbox: Add Aspeed ast2400/2500 bindings Cyril Bur
2017-01-12  0:29     ` Cyril Bur
     [not found]     ` <20170112002910.3650-2-cyrilbur-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-01-18 20:38       ` Rob Herring
2017-01-18 20:38         ` Rob Herring
2017-01-19  0:05         ` Cyril Bur
2017-01-19  0:05           ` Cyril Bur
     [not found]           ` <1484784318.4097.2.camel-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-01-19 15:08             ` Benjamin Herrenschmidt
2017-01-19 15:08               ` Benjamin Herrenschmidt
2017-01-12  0:29   ` [PATCH 2/4] Documentation: dt: misc: Add Aspeed ast2400/2500 LPC Control bindings Cyril Bur
2017-01-12  0:29     ` Cyril Bur
     [not found]     ` <20170112002910.3650-3-cyrilbur-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-01-18 21:16       ` Rob Herring
2017-01-18 21:16         ` Rob Herring
2017-01-19  0:19         ` Cyril Bur
2017-01-19  0:19           ` Cyril Bur
2017-01-12  0:29   ` [PATCH 3/4] drivers/misc: Add ASpeed LPC control driver Cyril Bur
2017-01-12  0:29     ` Cyril Bur
     [not found]     ` <20170112002910.3650-4-cyrilbur-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-01-12  7:43       ` Greg KH
2017-01-12  7:43         ` Greg KH
     [not found]         ` <20170112074312.GA23943-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2017-01-12 15:36           ` Benjamin Herrenschmidt
2017-01-12 15:36             ` Benjamin Herrenschmidt
2017-01-12  7:47       ` Greg KH
2017-01-12  7:47         ` Greg KH
     [not found]         ` <20170112074750.GB23943-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2017-01-12 10:16           ` Cyril Bur
2017-01-12 10:16             ` Cyril Bur
     [not found]             ` <1484216163.11416.8.camel-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-01-12 10:30               ` Greg KH
2017-01-12 10:30                 ` Greg KH
     [not found]                 ` <20170112103038.GA19239-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2017-01-12 15:27                   ` Benjamin Herrenschmidt
2017-01-12 15:27                     ` Benjamin Herrenschmidt
     [not found]                     ` <1484234867.2492.39.camel-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
2017-01-12 16:00                       ` Greg KH
2017-01-12 16:00                         ` Greg KH
     [not found]                         ` <20170112160051.GB8095-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2017-01-12 16:07                           ` Benjamin Herrenschmidt
2017-01-12 16:07                             ` Benjamin Herrenschmidt
     [not found]                             ` <1484237253.2492.43.camel-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
2017-01-12 16:26                               ` Greg KH [this message]
2017-01-12 16:26                                 ` Greg KH
     [not found]                                 ` <20170112162619.GB10283-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2017-01-12 16:31                                   ` Benjamin Herrenschmidt
2017-01-12 16:31                                     ` Benjamin Herrenschmidt
2017-01-12 15:35               ` Benjamin Herrenschmidt
2017-01-12 15:35                 ` Benjamin Herrenschmidt
     [not found]                 ` <1484235315.2492.41.camel-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
2017-01-12 16:27                   ` Greg KH
2017-01-12 16:27                     ` Greg KH
2017-01-12 16:29                   ` Benjamin Herrenschmidt
2017-01-12 16:29                     ` Benjamin Herrenschmidt
     [not found]                     ` <1484238577.2492.45.camel-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
2017-01-12 17:27                       ` Greg KH
2017-01-12 17:27                         ` Greg KH
2017-01-12  0:29   ` [PATCH 4/4] drivers/mailbox: Add ASpeed mailbox driver Cyril Bur
2017-01-12  0:29     ` Cyril Bur
     [not found]     ` <20170112002910.3650-5-cyrilbur-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-02-07  5:40       ` Joel Stanley
2017-02-07  5:40         ` Joel Stanley
     [not found]         ` <CACPK8XcsScjrit-7VHh4oL=zPiMeEAB5_R550U0uPsuQ4WF1mg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-02-07  5:44           ` Benjamin Herrenschmidt
2017-02-07  5:44             ` Benjamin Herrenschmidt
2017-02-07 22:57           ` Cyril Bur
2017-02-07 22:57             ` Cyril Bur
     [not found]             ` <1486508229.3824.1.camel-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2017-02-07 22:59               ` Joel Stanley
2017-02-07 22:59                 ` Joel Stanley

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