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linux/drivers/gpu/drm
Chris Wilson e29bb4ebbf drm/i915: Use a temporary va_list for two-pass string handling
In

commit edc3d8848d
Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Date:   Thu May 23 13:55:35 2013 +0300

    drm/i915: avoid big kmallocs on reading error state

we introduce a two-pass mechanism for splitting long strings being
formatted into the error-state. The first pass finds the length, and the
second pass emits the right portion of the string into the accumulation
buffer. Unfortunately we use the same va_list for both passes, resulting
in the second pass reading garbage off the end of the argument list. As
the two passes are only used for boundaries between read() calls, the
corruption is only rarely seen.

This fixes the root cause behind

commit baf27f9b17
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Sat Jun 29 23:26:50 2013 +0100

    drm/i915: Break up the large vsnprintf() in print_error_buffers()

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2013-09-24 09:36:40 +02:00
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************************************************************
* For the very latest on DRI development, please see:      *
*     http://dri.freedesktop.org/                          *
************************************************************

The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).

The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:

    1. The DRM provides synchronized access to the graphics hardware via
       the use of an optimized two-tiered lock.

    2. The DRM enforces the DRI security policy for access to the graphics
       hardware by only allowing authenticated X11 clients access to
       restricted regions of memory.

    3. The DRM provides a generic DMA engine, complete with multiple
       queues and the ability to detect the need for an OpenGL context
       switch.

    4. The DRM is extensible via the use of small device-specific modules
       that rely extensively on the API exported by the DRM module.


Documentation on the DRI is available from:
    http://dri.freedesktop.org/wiki/Documentation
    http://sourceforge.net/project/showfiles.php?group_id=387
    http://dri.sourceforge.net/doc/

For specific information about kernel-level support, see:

    The Direct Rendering Manager, Kernel Support for the Direct Rendering
    Infrastructure
    http://dri.sourceforge.net/doc/drm_low_level.html

    Hardware Locking for the Direct Rendering Infrastructure
    http://dri.sourceforge.net/doc/hardware_locking_low_level.html

    A Security Analysis of the Direct Rendering Infrastructure
    http://dri.sourceforge.net/doc/security_low_level.html