[PATCH] HID: intel-thc-hid: intel-quickspi: validate report size before copy

[HyeongJun An <sammiee5311@gmail.com>]

write_cmd_to_txdma() builds an output report in qsdev->report_buf, a heap
buffer allocated in quickspi_alloc_report_buf() to the device-descriptor
derived max_report_len (a few hundred bytes for a touch controller).  It
copies the caller-supplied report into that buffer:

	memcpy(write_buf->content, report_buf, report_buf_len);

The HID core caps a report at HID_MAX_BUFFER_SIZE (16384) by default, and
quickspi_hid_ll_driver does not set max_buffer_size, so the length reaches
the driver unbounded.  A hidraw SET_REPORT/SET_FEATURE ioctl carrying a
report larger than max_report_len therefore overflows report_buf with
attacker-controlled length and content.

Record the report_buf allocation size and reject reports that do not fit
before copying, matching the equivalent guard in the intel-quicki2c
sibling (quicki2c_init_write_buf()) and the hid-goodix-spi fix.

Fixes: 9d8d51735a3a ("HID: intel-thc-hid: intel-quickspi: Add HIDSPI protocol implementation")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: HyeongJun An <sammiee5311@gmail.com>
---
 drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c      | 2 ++
 drivers/hid/intel-thc-hid/intel-quickspi/quickspi-dev.h      | 1 +
 drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.c | 3 +++
 3 files changed, 6 insertions(+)

diff --git a/drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c b/drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c
index 4ae2e1718b30..1695efd5961d 100644
--- a/drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c
+++ b/drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c
@@ -559,6 +559,8 @@ static int quickspi_alloc_report_buf(struct quickspi_device *qsdev)
 	if (!qsdev->report_buf)
 		return -ENOMEM;
 
+	qsdev->report_buf_size = max_report_len;
+
 	return 0;
 }
 
diff --git a/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-dev.h b/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-dev.h
index bf5e18f5a5f4..0ed964bfe3dd 100644
--- a/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-dev.h
+++ b/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-dev.h
@@ -157,6 +157,7 @@ struct quickspi_device {
 	u8 *report_descriptor;
 	u8 *input_buf;
 	u8 *report_buf;
+	u32 report_buf_size;
 	u32 report_len;
 
 	wait_queue_head_t reset_ack_wq;
diff --git a/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.c b/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.c
index cb19057f1191..db6054843e77 100644
--- a/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.c
+++ b/drivers/hid/intel-thc-hid/intel-quickspi/quickspi-protocol.c
@@ -30,6 +30,9 @@ static int write_cmd_to_txdma(struct quickspi_device *qsdev,
 
 	write_buf = (struct output_report *)qsdev->report_buf;
 
+	if (HIDSPI_OUTPUT_REPORT_SIZE(report_buf_len) > qsdev->report_buf_size)
+		return -EINVAL;
+
 	write_buf->output_hdr.report_type = report_type;
 	write_buf->output_hdr.content_len = cpu_to_le16(report_buf_len);
 	write_buf->output_hdr.content_id = report_id;
-- 
2.43.0