Messages in this thread | | | From | Linus Torvalds <> | Date | Sun, 20 Jun 2021 09:37:47 -0700 | Subject | Re: [PATCH] Input: joydev - prevent potential write out of bounds in ioctl |
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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
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