[Bug 66077] Oops reading i915_error_state

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=66077

--- Comment #3 from Mika Kuoppala <mika.kuoppala at intel.com> ---
commit e29bb4ebbf000ff9ac081d29784a3331618f012e
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Fri Sep 20 10:20:59 2013 +0100

    drm/i915: Use a temporary va_list for two-pass string handling

    In

    commit edc3d8848dc9fe2a470316363dab8ef211d77e01
    Author: Mika Kuoppala <mika.kuoppala at 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 baf27f9b17bf2f369f3865e38c41d2163e8d815d
    Author: Chris Wilson <chris at 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 at chris-wilson.co.uk>
    Cc: Mika Kuoppala <mika.kuoppala at intel.com>
    Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
    Cc: stable at vger.kernel.org
    Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

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