From 66725039f7090afe14c31bd259e2059a68f04023 Mon Sep 17 00:00:00 2001 From: Bryam Vargas Date: Sun, 14 Jun 2026 14:19:43 -0700 Subject: [PATCH] Input: mms114 - reject an oversized device packet size mms114_interrupt() reads a packet of touch data from the device into a fixed-size on-stack buffer struct mms114_touch touch[MMS114_MAX_TOUCH]; which holds MMS114_MAX_TOUCH (10) events of MMS114_EVENT_SIZE (8) bytes, i.e. 80 bytes. The length of the I2C read into it is taken verbatim from the device: packet_size = mms114_read_reg(data, MMS114_PACKET_SIZE); if (packet_size <= 0) goto out; ... error = __mms114_read_reg(data, MMS114_INFORMATION, packet_size, (u8 *)touch); packet_size is a single device register byte (0x0F) and the only check is the lower bound packet_size <= 0; it is never bounded against the size of touch[]. A malfunctioning, malicious or counterfeit controller (or an attacker tampering with the I2C bus) can report a packet_size of up to 255, so __mms114_read_reg() writes up to 175 bytes past the end of touch[] on the IRQ-thread stack: a stack out-of-bounds write that can overwrite the stack canary, saved registers and the return address. A well-formed device never reports more than the buffer holds, so reject an oversized packet and drop the report, consistent with the handler's other error paths, rather than reading past the buffer. Fixes: 07b8481d4aff ("Input: add MELFAS mms114 touchscreen driver") Signed-off-by: Bryam Vargas Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260612-b4-disp-dc4b8dc4-v1-1-d7cb0a828d92@proton.me Signed-off-by: Dmitry Torokhov --- drivers/input/touchscreen/mms114.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/input/touchscreen/mms114.c b/drivers/input/touchscreen/mms114.c index 9597214d9d3c..4d748a13408d 100644 --- a/drivers/input/touchscreen/mms114.c +++ b/drivers/input/touchscreen/mms114.c @@ -226,6 +226,12 @@ static irqreturn_t mms114_interrupt(int irq, void *dev_id) if (packet_size <= 0) goto out; + if (packet_size > sizeof(touch)) { + dev_err(&client->dev, "Invalid packet size %d (max %zu)\n", + packet_size, sizeof(touch)); + goto out; + } + /* MMS136 has slightly different event size */ if (data->type == TYPE_MMS134S || data->type == TYPE_MMS136) touch_size = packet_size / MMS136_EVENT_SIZE;