Messages in this thread | | | Date | Mon, 23 Nov 2009 18:46:46 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] vt: Don't exceed max_font_size on copy in con_font_get() |
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On Mon, 23 Nov 2009 21:23:42 +0100 Roel Kluin <roel.kluin@gmail.com> wrote:
> font.data is kmallocd with max_font_size (defined 65536). Below occurs a > copy_to_user with `c' as a size argument. Ensure we don't copy too much. > > Signed-off-by: Roel Kluin <roel.kluin@gmail.com> > --- > drivers/char/vt.c | 4 ++++ > 1 files changed, 4 insertions(+), 0 deletions(-) > > If it is possible for c to be greater than 65536 then I think we may need this. > Correct? > > diff --git a/drivers/char/vt.c b/drivers/char/vt.c > index 0c80c68..045af83 100644 > --- a/drivers/char/vt.c > +++ b/drivers/char/vt.c > @@ -3861,6 +3861,10 @@ static int con_font_get(struct vc_data *vc, struct console_font_op *op) > goto out; > > c = (font.width+7)/8 * 32 * font.charcount; > + if (c > max_font_size) { > + rc = -EINVAL; > + goto out; > + } > > if (op->data && font.charcount > op->charcount) > rc = -ENOSPC;
Perhaps it is impossible for `c' to exceed max_font_size here. The check in con_font_set() will prevent it.
There are probably other places in the kernel which initialise a console_font_op, and perhaps one of those is buggy - I didn't check.
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