Commit 566f9c9f authored Jul 30, 2022 by Helge Deller Committed by Greg Kroah-Hartman Aug 30, 2022

vt: Clear selection before changing the font



When changing the console font with ioctl(KDFONTOP) the new font size
can be bigger than the previous font. A previous selection may thus now
be outside of the new screen size and thus trigger out-of-bounds
accesses to graphics memory if the selection is removed in
vc_do_resize().

Prevent such out-of-memory accesses by dropping the selection before the
various con_font_set() console handlers are called.

Reported-by:  <syzbot+14b0e8f3fd1612e35350@syzkaller.appspotmail.com>
Cc: stable <stable@kernel.org>
Tested-by: Khalid Masum <khalid.masum.92@gmail.com>
Signed-off-by: Helge Deller <deller@gmx.de>
Link: https://lore.kernel.org/r/YuV9apZGNmGfjcor@p100


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent b5a5b9d5

drivers/tty/vt/vt.c

+8 −4

Original line number	Diff line number	Diff line
		@@ -4662,9 +4662,11 @@ static int con_font_set(struct vc_data vc, struct console_font_op op)
		console_lock();
		if (vc->vc_mode != KD_TEXT)
		rc = -EINVAL;
		else if (vc->vc_sw->con_font_set)
		else if (vc->vc_sw->con_font_set) {
		if (vc_is_sel(vc))
		clear_selection();
		rc = vc->vc_sw->con_font_set(vc, &font, op->flags);
		else
		} else
		rc = -ENOSYS;
		console_unlock();
		kfree(font.data);
		@@ -4691,9 +4693,11 @@ static int con_font_default(struct vc_data vc, struct console_font_op op)
		console_unlock();
		return -EINVAL;
		}
		if (vc->vc_sw->con_font_default)
		if (vc->vc_sw->con_font_default) {
		if (vc_is_sel(vc))
		clear_selection();
		rc = vc->vc_sw->con_font_default(vc, &font, s);
		else
		} else
		rc = -ENOSYS;
		console_unlock();
		if (!rc) {