From 414edcd32aa54bad8827e7c74cace168006c5fab Mon Sep 17 00:00:00 2001 From: "Antonino A. Daplas" Date: Tue, 6 Sep 2005 15:17:52 -0700 Subject: [PATCH] [PATCH] vt: fix possible memory corruption in complement_pos Based on a patch from Andr Pereira de Almeida It might be possible for the saved pointer (*p) to become invalid in between vc_resizes, so saving the screen offset instead of the screen pointer is saner. This bug is very hard to trigger though, but Andre probably did, if he's submitting this patch. Anyway, with Andre's patch, it's still possible for the offsets to be still illegal, if the new screen size is smaller than the old one. So I've also added checks if the offsets are still within the screenbuffer size. Signed-off-by: Antonino Daplas Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/char/vt.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/drivers/char/vt.c b/drivers/char/vt.c index 27b6c297906a..b8d0c290b0db 100644 --- a/drivers/char/vt.c +++ b/drivers/char/vt.c @@ -434,21 +434,25 @@ void invert_screen(struct vc_data *vc, int offset, int count, int viewed) /* used by selection: complement pointer position */ void complement_pos(struct vc_data *vc, int offset) { - static unsigned short *p; + static int old_offset = -1; static unsigned short old; static unsigned short oldx, oldy; WARN_CONSOLE_UNLOCKED(); - if (p) { - scr_writew(old, p); + if (old_offset != -1 && old_offset >= 0 && + old_offset < vc->vc_screenbuf_size) { + scr_writew(old, screenpos(vc, old_offset, 1)); if (DO_UPDATE(vc)) vc->vc_sw->con_putc(vc, old, oldy, oldx); } - if (offset == -1) - p = NULL; - else { + + old_offset = offset; + + if (offset != -1 && offset >= 0 && + offset < vc->vc_screenbuf_size) { unsigned short new; + unsigned short *p; p = screenpos(vc, offset, 1); old = scr_readw(p); new = old ^ vc->vc_complement_mask; @@ -459,6 +463,7 @@ void complement_pos(struct vc_data *vc, int offset) vc->vc_sw->con_putc(vc, new, oldy, oldx); } } + } static void insert_char(struct vc_data *vc, unsigned int nr) -- 2.20.1