tty vt: fix character insertion overflow

commit a883b70d8e0a88278c0a1f80753b4dc99962b541 upstream.

Commit 81732c3b2fed ("tty vt: Fix line garbage in virtual console on
command line edition") broke insert_char() in multiple ways.  Then
commit b1a925f44a3a ("tty vt: Fix a regression in command line edition")
partially fixed it.  However, the buffer being moved is still too large
and overflowing beyond the end of the current line, corrupting existing
characters on the next line.

Example test case:

echo -e "abc\nde\x1b[A\x1b[4h \x1b[4l\x1b[B"

Expected result:

ab c
de

Current result:

ab c
 e

Needless to say that this is very annoying when inserting words in the
middle of paragraphs with certain text editors.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 8fd89687d068e58b5546a153f8ea894c32782f47..3614c9c033c3597fc8e8b048c7bc870121cc3b2d 100644 (file)
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -539,7 +539,7 @@ static void insert_char(struct vc_data *vc, unsigned int nr)
 {
        unsigned short *p = (unsigned short *) vc->vc_pos;
 
-       scr_memmovew(p + nr, p, (vc->vc_cols - vc->vc_x) * 2);
+       scr_memmovew(p + nr, p, (vc->vc_cols - vc->vc_x - nr) * 2);
        scr_memsetw(p, vc->vc_video_erase_char, nr * 2);
        vc->vc_need_wrap = 0;
        if (DO_UPDATE(vc))