On Sun, Jun 20, 2021 at 09:37:47AM -0700, Linus Torvalds wrote: > 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"). 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; > > out: > kfree(keypam); > > (whitespace-damaged, I would like Dmitry to think about it rather than > apply this mindlessly. > > Dmitry? 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? Thanks. -- Dmitry
