In the Linux kernel, the following vulnerability has been resolved:
Input: evdev - zero absinfo before partial copy in EVIOCSABS
The EVIOCSABS handler copies at most the user supplied ioctl size into an uninitialized on-stack struct input_absinfo:
if (copy_from_user(&abs, p, min_t(size_t, size, sizeof(struct input_absinfo))))
The size comes from _IOC_SIZE() of the ioctl command and is therefore fully controlled by userspace. A short size leaves the trailing part of the structure holding whatever was on the kernel stack, and the whole structure is then stored into the device:
dev->absinfo[t] = abs;
EVIOCGABS hands that back to userspace, disclosing the stale stack bytes. Only the resolution field is currently cleared, which covers the legacy struct layout but not an arbitrarily short size.
Zero the structure before the copy so any part not supplied by the caller reads back as zero. The existing resolution fixup is kept, since it also handles a size that partially overlaps that field.
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