From: Linus Torvalds <torvalds@linux-foundation.org>
To: Alexander Larkin <avlarkin82@gmail.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Dan Carpenter <dan.carpenter@oracle.com>,
linux-input@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>,
Security Officers <security@kernel.org>,
Murray McAllister <murray.mcallister@gmail.com>
Subject: Re: [PATCH] Input: joydev - prevent potential write out of bounds in ioctl
Date: Sun, 20 Jun 2021 09:37:47 -0700 [thread overview]
Message-ID: <CAADWXX-fpcPh+jGX7=Hbkqr7yhwzbUT915NBBzqHGecFVbxmzw@mail.gmail.com> (raw)
In-Reply-To: <20210620120030.1513655-1-avlarkin82@gmail.com>
On Sun, Jun 20, 2021 at 5:01 AM Alexander Larkin <avlarkin82@gmail.com> 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
validated).
> 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[1]" 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").
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;
out:
kfree(keypam);
(whitespace-damaged, I would like Dmitry to think about it rather than
apply this mindlessly.
Dmitry?
Linus
next prev parent reply other threads:[~2021-06-20 16:42 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 [this message]
2021-06-21 5:25 ` Dmitry Torokhov
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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