In the Linux kernel, the following vulnerability has been resolved: Input: cs40l50-vibra -...

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

Input: cs40l50-vibra - validate custom data from user space

cs40l50_add() copies the custom data of an FF_PERIODIC/FF_CUSTOM effect straight from the ff_effect the user passed to EVIOCSFF, without requiring it to hold anything:

work_data.custom_data = memdup_array_user(periodic->custom_data,
                                          periodic->custom_len,
                                          sizeof(s16));
work_data.custom_len = periodic->custom_len;

The driver then reads two words out of that buffer: custom_data[0] as the waveform bank in cs40l50_effect_bank_set(), and custom_data[1] as the index within the bank in cs40l50_effect_index_set(). Neither read is covered by a length check, and custom_len is fully user controlled:

• custom_len == 0 makes memdup_array_user() call memdup_user() with a length of zero, which returns ZERO_SIZE_PTR rather than an error, so custom_data[0] dereferences it.

• custom_len == 1 allocates two bytes. A bank of ROM or RAM keeps effect->type out of the OWT case, and custom_data[1] is then read one word past the allocation.

The bank value itself is also mishandled. It is masked with CS40L50_CUSTOM_DATA_MASK (0xffff) but stored in an s16, so a custom_data[0] of 0x8000 or above wraps to a negative value that passes the "bank_type >= CS40L50_WVFRM_BANK_NUM" test. cs40l50_effect_index_set() indexes vib->dsp.banks[] with it before the switch statement's default case gets a chance to reject it:

base_index = vib->dsp.banks[effect->type].base_index;
max_index = vib->dsp.banks[effect->type].max_index;

Require the two words the driver reads to be present, and hold the masked bank in a u32 so the existing upper-bound test covers the whole range. The da7280 haptic driver already range checks custom_len this way.