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vgacon: Prevent faulty bootparams.screeninfo from causing harm

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If a zero for the number of colums or rows manages to slip through,
gotoxy() will underflow vc->vc_pos, causing the next action on the
referenced memory to end with a page fault.

Make the check in vgacon_startup() more pessimistic to prevent that.

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
This commit is contained in:
Jan H. Schönherr 2017-09-04 16:00:50 +02:00 committed by Bartlomiej Zolnierkiewicz
parent 58ec01ceba
commit b9a58de545
1 changed files with 2 additions and 3 deletions
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5
drivers/video/console/vgacon.c
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@ -398,9 +398,8 @@ static const char *vgacon_startup(void)
#endif
}
/* boot_params.screen_info initialized? */
if ((screen_info.orig_video_mode == 0) &&
(screen_info.orig_video_lines == 0) &&
/* boot_params.screen_info reasonably initialized? */
if ((screen_info.orig_video_lines == 0) ||
(screen_info.orig_video_cols == 0))
goto no_vga;