Messages in this thread Patch in this message | | | From | Nicolas Pitre <> | Subject | [PATCH 1/3] vt: avoid a VLA in the unicode screen scroll function | Date | Tue, 17 Jul 2018 21:02:40 -0400 |
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The nr argument is typically small: most often nr == 1. However this could be abused with a very large explicit scroll in a resized screen. Make the code scroll lines one at a time in all cases to avoid the VLA. Anything smarter is most likely not warranted here.
Requested-by: Kees Cook <keescook@chromium.org> Signed-off-by: Nicolas Pitre <nico@linaro.org> --- drivers/tty/vt/vt.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 2d14bb195d..03e79f7787 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -433,20 +433,22 @@ static void vc_uniscr_scroll(struct vc_data *vc, unsigned int t, unsigned int b, if (uniscr) { unsigned int s, d, rescue, clear; - char32_t *save[nr]; s = clear = t; - d = t + nr; - rescue = b - nr; + d = t + 1; + rescue = b - 1; if (dir == SM_UP) { swap(s, d); swap(clear, rescue); } - memcpy(save, uniscr->lines + rescue, nr * sizeof(*save)); - memmove(uniscr->lines + d, uniscr->lines + s, - (b - t - nr) * sizeof(*uniscr->lines)); - memcpy(uniscr->lines + clear, save, nr * sizeof(*save)); - vc_uniscr_clear_lines(vc, clear, nr); + while (nr--) { + char32_t *tmp; + tmp = uniscr->lines[rescue]; + memmove(uniscr->lines + d, uniscr->lines + s, + (b - t - 1) * sizeof(*uniscr->lines)); + uniscr->lines[clear] = tmp; + vc_uniscr_clear_lines(vc, clear, 1); + } } } -- 2.17.1
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