[bug #24154] [patch] Wrong implementation of grub_video_vbe_scroll

[Tomas Tintera]

URL:
  <http://savannah.gnu.org/bugs/?24154>

                 Summary: [patch] Wrong implementation of
grub_video_vbe_scroll
                 Project: GNU GRUB
            Submitted by: trosos
            Submitted on: Thu 28 Aug 2008 10:03:07 AM GMT
                Category: None
                Severity: Major
                Priority: 5 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: Tomas Tintera
        Originator Email: address@hidden
             Open/Closed: Open
         Discussion Lock: Any
                 Release: svn-2008-08-28
         Reproducibility: None
         Planned Release: 

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Details:

Hi all,

while reading the source, I noticed that the
grub_video_vbe_scroll function seems not to work if used
with 0 < dy < (render_target->viewport.height / 2).
If we scroll down, we must begin at the bottom and continue
upwards, or else we would overwrite some memory before we
read it, which would give undesirable results (please
correct me if I am wrong).

(However, this situation so far never happens (because
grub_video_vbe_scroll() is only used to scroll up the text),
leaving this bug unreproducible).


The patch is attached.

In the patch, I changed the type of the variable j, thinking
that it is a mistype, as I noticed you use the type unit32_t
in that context anywhere else.


Best regards,
Tomas "trosos" Tintera




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File Attachments:


-------------------------------------------------------
Date: Thu 28 Aug 2008 10:03:07 AM GMT  Name: vbe.diff  Size: 2kB   By: trosos

<http://savannah.gnu.org/bugs/download.php?file_id=16376>

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