linux-kernel - Re: [PATCH] fbcon: Fix vc attr at deinit

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]

Date:   Thu, 5 Jan 2017 14:26:07 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...com>
To:     Takashi Iwai <tiwai@...e.de>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.cz>, <linux-fbdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] fbcon: Fix vc attr at deinit

On 04/01/17 15:50, Takashi Iwai wrote:
> On Tue, 03 Jan 2017 16:03:22 +0100,
> Takashi Iwai wrote:
>>
>> fbcon can deal with vc_hi_font_mask (the upper 256 chars) and adjust
>> the vc attrs dynamically when vc_hi_font_mask is changed at
>> fbcon_init().  When the vc_hi_font_mask is set, it remaps the attrs in
>> the existing console buffer with one bit shift up (for 9 bits), while
>> it remaps with one bit shift down (for 8 bits) when the value is
>> cleared.  It works fine as long as the font gets updated after fbcon
>> was initialized.
>>
>> However, we hit a bizarre problem when the console is switched to
>> another fb driver (typically from vesafb or efifb to drmfb).  At
>> switching to the new fb driver, we temporarily rebind the console to
>> the dummy console, then rebind to the new driver.  During the
>> switching, we leave the modified attrs as is.  Thus, the new fbcon
>> takes over the old buffer as if it were to contain 8 bits chars
>> (although the attrs are still shifted for 9 bits), and effectively
>> this results in the yellow color texts instead of the original white
>> color, as found in the bugzilla entry below.
>>
>> An easy fix for this is to re-adjust the attrs before leaving the
>> fbcon at con_deinit callback.  Since the code to adjust the attrs is
>> already present in the current fbcon code, in this patch, we simply
>> factor out the relevant code, and call it from fbcon_deinit().
>>
>> Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=1000619
>> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> 
> Actually not only checkpatch but also I can't find the proper
> maintainer for this...
> 
> Tomi, could you check and take if it's OK?
> 
> Ideally, this kind of stuff should have been in rather vt side, I
> suppose.  But since the code is already present in fbcon, it's easier
> to reuse it as a fix for now.

I'm not fbdev maintainer anymore. Added Bartlomiej (and Andrew).

 Tomi



Download attachment "signature.asc" of type "application/pgp-signature" (820 bytes)