tree 4c4861b54b2c1529c4677e6d31bb6027568aaa1a
parent eed74dfcd48101d259012ac08d29061eea500249
author Antonino A. Daplas <[EMAIL PROTECTED]> Wed, 07 Sep 2005 05:17:52 -0700
committer Linus Torvalds <[EMAIL PROTECTED]> Thu, 08 Sep 2005 06:57:36 -0700

[PATCH] vt: fix possible memory corruption in complement_pos

Based on a patch from Andr Pereira de Almeida <[EMAIL PROTECTED]>

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 <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>

 drivers/char/vt.c |   17 +++++++++++------
 1 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/char/vt.c b/drivers/char/vt.c
--- a/drivers/char/vt.c
+++ b/drivers/char/vt.c
@@ -434,21 +434,25 @@ void invert_screen(struct vc_data *vc, i
 /* 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, 
                        vc->vc_sw->con_putc(vc, new, oldy, oldx);
                }
        }
+
 }
 
 static void insert_char(struct vc_data *vc, unsigned int nr)
-
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