5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Iván Ezequiel Rodriguez commit f84819ef8d66931ee3998fee3c4f03230f4cb6cc upstream. 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: compat_effect = (struct ff_effect_compat *)effect; if (copy_from_user(compat_effect, buffer, 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. Fixes: 2d56f3a32c0e ("Input: refactor evdev 32bit compat to be shareable with uinput") Cc: stable@vger.kernel.org Signed-off-by: Iván Ezequiel Rodriguez Link: https://patch.msgid.link/20260901130629.24078-3-ivanrwcm25@gmail.com Signed-off-by: Dmitry Torokhov Signed-off-by: Greg Kroah-Hartman --- drivers/input/input-compat.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/input/input-compat.c +++ b/drivers/input/input-compat.c @@ -75,6 +75,8 @@ int input_ff_effect_from_user(const char */ compat_effect = (struct ff_effect_compat *)effect; + memset(effect, 0, sizeof(*effect)); + if (copy_from_user(compat_effect, buffer, sizeof(struct ff_effect_compat))) return -EFAULT;