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tty: Clean console safely 

Traditional \E[2J sequence erases console display but scroll-back
buffer and underlying device (frame) buffer keep data that can be
accessed by scrolling console back.

This patch introduce new \E[J parameter 3 that allows to scramble
scroll-back buffer explicitly. Session locking programs (screen,
vlock) can use it to prevent attacker to browse locked console
history.

Signed-off-by: Petr Písař <ppisar@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Petr Písař 2011-04-15 10:08:08 +02:00 committed by Greg Kroah-Hartman
parent d942060288
commit f8df13e0a9
1 changed files with 7 additions and 0 deletions
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7
drivers/tty/vt/vt.c
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@ -1193,6 +1193,13 @@ static void csi_J(struct vc_data *vc, int vpar)
vc->vc_x + 1);
}
break;
case 3: /* erase scroll-back buffer (and whole display) */
scr_memsetw(vc->vc_screenbuf, vc->vc_video_erase_char,
vc->vc_screenbuf_size >> 1);
set_origin(vc);
if (CON_IS_VISIBLE(vc))
update_screen(vc);
/* fall through */
case 2: /* erase whole display */
count = vc->vc_cols * vc->vc_rows;
start = (unsigned short *)vc->vc_origin;