From: Antonino A. Daplas Date: Tue, 8 May 2007 07:40:06 +0000 (-0700) Subject: vgacon: disallow console operations when in KD_GRAPHICS mode X-Git-Tag: v2.6.22-rc1~369 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2ae854777592856ad8ce4d4cdb6114804e2e28f6;p=linux-2.6 vgacon: disallow console operations when in KD_GRAPHICS mode Reported by James Pearson as: boot to run level 3 if not root, then make sure /dev/console is writeable login and type: setterm -blank 0 start X type into an xterm: while true; do echo "" > /dev/console; usleep 100000; done while the above loop is running switch to the text console and back again (Ctrl-Alt-F1 then Ctrl-Alt-F7) ... and the screen will be shifting (and wrapping) to the left. This problem stems from continuously writing text to the system console (which is in KD_TEXT mode) while the foreground console is in KD_GRAPHICS mode. Somewhere along the way, console printing got confused and omitted the KD_GRAPHICS/KD_TEXT test. Thus, vgacon attempted to scroll the screen of X, which causes X to shift. Fix by disallowing vgacon to touch the hardware when the vc is in KD_GRAPHICS mode. A definitive fix entails a full audit of the console code. Signed-off-by: Antonino Daplas Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c index d0d2733ef4..2460b82a1d 100644 --- a/drivers/video/console/vgacon.c +++ b/drivers/video/console/vgacon.c @@ -660,6 +660,9 @@ static void vgacon_set_cursor_size(int xpos, int from, int to) static void vgacon_cursor(struct vc_data *c, int mode) { + if (c->vc_mode != KD_TEXT) + return; + vgacon_restore_screen(c); switch (mode) { @@ -1318,7 +1321,7 @@ static int vgacon_scroll(struct vc_data *c, int t, int b, int dir, unsigned long oldo; unsigned int delta; - if (t || b != c->vc_rows || vga_is_gfx) + if (t || b != c->vc_rows || vga_is_gfx || c->vc_mode != KD_TEXT) return 0; if (!vga_hardscroll_enabled || lines >= c->vc_rows / 2)