On Sun, Jun 20, 2021 at 5:01 AM Alexander Larkin <avlarkin82@xxxxxxxxx> 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
