fbcon: Prevent that screen size is smaller than font size

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We need to prevent that users configure a screen size which is smaller than the
currently selected font size. Otherwise rendering chars on the screen will
access memory outside the graphics memory region.

This patch adds a new function fbcon_modechange_possible() which
implements this check and which later may be extended with other checks
if necessary.  The new function is called from the FBIOPUT_VSCREENINFO
ioctl handler in fbmem.c, which will return -EINVAL if userspace asked
for a too small screen size.

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: stable@vger.kernel.org # v5.4+

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This commit is contained in:

Helge Deller 2022-06-25 13:00:34 +02:00

parent 65a01e601d

commit e64242caef

3 changed files with 35 additions and 1 deletions

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include/linux/fbcon.h

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