[PATCH] Input: cs40l50-vibra - validate custom data from user space

[HyeongJun An <sammiee5311@gmail.com>]

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.

Fixes: c38fe1bb5d21 ("Input: cs40l50 - Add support for the CS40L50 haptic driver")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: HyeongJun An <sammiee5311@gmail.com>
---
 drivers/input/misc/cs40l50-vibra.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/input/misc/cs40l50-vibra.c b/drivers/input/misc/cs40l50-vibra.c
index 996d6c38cca4..7ef4534fea2f 100644
--- a/drivers/input/misc/cs40l50-vibra.c
+++ b/drivers/input/misc/cs40l50-vibra.c
@@ -139,10 +139,10 @@ static struct cs40l50_effect *cs40l50_find_effect(int id, struct list_head *effe
 static int cs40l50_effect_bank_set(struct cs40l50_work *work_data,
 				   struct cs40l50_effect *effect)
 {
-	s16 bank_type = work_data->custom_data[0] & CS40L50_CUSTOM_DATA_MASK;
+	u32 bank_type = work_data->custom_data[0] & CS40L50_CUSTOM_DATA_MASK;
 
 	if (bank_type >= CS40L50_WVFRM_BANK_NUM) {
-		dev_err(work_data->vib->dev, "Invalid bank (%d)\n", bank_type);
+		dev_err(work_data->vib->dev, "Invalid bank (%u)\n", bank_type);
 		return -EINVAL;
 	}
 
@@ -326,6 +326,12 @@ static int cs40l50_add(struct input_dev *dev, struct ff_effect *effect,
 		return -EINVAL;
 	}
 
+	if (periodic->custom_len < CS40L50_OWT_CUSTOM_DATA_SIZE) {
+		dev_err(vib->dev, "Invalid custom data length (%u)\n",
+			periodic->custom_len);
+		return -EINVAL;
+	}
+
 	work_data.custom_data = memdup_array_user(effect->u.periodic.custom_data,
 						  effect->u.periodic.custom_len,
 						  sizeof(s16));
-- 
2.43.0