In the Linux kernel, the following vulnerability has been resolved: Input: zero ff_effect before compat copy in input_ff_effect_from_user

In the Linux kernel, the following vulnerability has been resolved:

Input: zero ff_effect before compat copy in input_ff_effect_from_user

In the compat path input_ff_effect_from_user() aliases the caller's
native struct ff_effect with the smaller struct ff_effect_compat and
copies only the compat sized prefix:

 1compat_effect = (struct ff_effect_compat *)effect;
 2 
 3if (copy_from_user(compat_effect, buffer,
 4		   sizeof(struct ff_effect_compat)))

The tail of the native structure is never written. Callers pass an
uninitialized on-stack object, for example evdev_do_ioctl() for
EVIOCSFF, so those bytes keep their previous stack contents.
input_ff_upload() then stores the full native structure in
ff->effects[id], from where a uinput based force feedback daemon can
read it back via UI_BEGIN_FF_UPLOAD, disclosing kernel stack memory to
userspace.

Zero the effect before the compat copy.