From: Dmitry Torokhov <firstname.lastname@example.org>
To: Linus Torvalds <email@example.com>
Cc: Alexander Larkin <firstname.lastname@example.org>,
Dan Carpenter <email@example.com>,
firstname.lastname@example.org, lkml <email@example.com>,
Security Officers <firstname.lastname@example.org>,
Murray McAllister <email@example.com>
Subject: Re: [PATCH] Input: joydev - prevent potential write out of bounds in ioctl
Date: Sun, 20 Jun 2021 22:25:08 -0700 [thread overview]
Message-ID: <YNAitJfOpoBkFitU@google.com> (raw)
On Sun, Jun 20, 2021 at 09:37:47AM -0700, Linus Torvalds wrote:
> On Sun, Jun 20, 2021 at 5:01 AM Alexander Larkin <firstname.lastname@example.org> wrote:
> > The problem is that the check of user input values that is just
> > before the fixed line of code is for the part of first values
> > (before len or before len/2), but then the usage of all the values
> > including i >= len (or i >= len/2) could be.
> No, I think the problem is simpler than that.
> > - for (i = 0; i < joydev->nabs; i++)
> > + for (i = 0; i < len && i < joydev->nabs; i++)
> > joydev->absmap[joydev->abspam[i]] = i;
> This part is unnecessary - all values of "joydev->abspam[i]" have been
> validated (either they are the old ones, or the new ones that we just
> > memcpy(joydev->keypam, keypam, len);
> > - for (i = 0; i < joydev->nkey; i++)
> > + for (i = 0; i < (len / 2) && i < joydev->nkey; i++)
> > joydev->keymap[keypam[i] - BTN_MISC] = i;
> The problem here is not that we walk past "len/2", but that the code
> *should* have used
> joydev->keymap[joydev->keypam[i] - BTN_MISC] = i;
> (note the "keypam" vs "joydev->keypam[i]").
> And the reason it *should* walk the whole "joydev->nkey" is that if
> there are later cases with the same keypam value, the later ones
> should override the previous ones (well, that "should" is more a
> "traditionally have").
Yes, we can discuss whether "short" ioctl should clear out the part of
map that is not supplied by the call, but given that I consider joydev
legacy my preference would be to leave this as it was.
> So I think the right patch is this one-liner
> diff --git a/drivers/input/joydev.c b/drivers/input/joydev.c
> index da8963a9f044..947d440a3be6 100644
> --- a/drivers/input/joydev.c
> +++ b/drivers/input/joydev.c
> @@ -499,7 +499,7 @@ static int joydev_handle_JSIOCSBTNMAP(struct
> joydev *joydev,
> memcpy(joydev->keypam, keypam, len);
> for (i = 0; i < joydev->nkey; i++)
> - joydev->keymap[keypam[i] - BTN_MISC] = i;
> + joydev->keymap[joydev->keypam[i] - BTN_MISC] = i;
> (whitespace-damaged, I would like Dmitry to think about it rather than
> apply this mindlessly.
Yes, this makes sense to me and it is safe as joydev->keypam is
guaranteed to be the right size.
Are you going to reformat this and resend or should I?
next prev parent reply other threads:[~2021-06-21 5:25 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-20 12:00 [PATCH] Input: joydev - prevent potential write out of bounds in ioctl Alexander Larkin
2021-06-20 16:37 ` Linus Torvalds
2021-06-21 5:25 ` Dmitry Torokhov [this message]
2021-06-21 15:45 ` Linus Torvalds
2021-06-21 20:06 ` Alexander Larkin
2021-06-21 21:30 ` Alexander Larkin
2021-06-21 21:32 ` Alexander Larkin
2021-06-21 22:38 ` Dmitry Torokhov
2021-07-03 16:21 ` Denis Efremov
2021-07-05 10:54 ` Dan Carpenter
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