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vt: Clear selection before changing the font

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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>
This commit is contained in:
Helge Deller 2022-07-30 20:50:18 +02:00 committed by Greg Kroah-Hartman
parent b5a5b9d5f2
commit 566f9c9f89
1 changed files with 8 additions and 4 deletions
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12
drivers/tty/vt/vt.c
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@ -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) {