[PATCH v2] HID: intel-thc-hid: intel-quickspi: validate report size before copy

[HyeongJun An]

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.

write_cmd_to_txdma() writes the output report header ahead of the content
in the same buffer, so size the allocation to cover the header as well.
That keeps the added bound from rejecting a maximum-sized report.

Fixes: 9d8d51735a3a ("HID: intel-thc-hid: intel-quickspi: Add HIDSPI protocol implementation")
Cc: stable@xxxxxxxxxxxxxxx
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: HyeongJun An <sammiee5311@xxxxxxxxx>
---
v2: Size report_buf to cover the output report header as well, so the added
    bound cannot reject a valid maximum-sized report (raised by the Sashiko
    AI review of v1).  No other change.

v1: https://lore.kernel.org/all/20260628133717.941389-1-sammiee5311@xxxxxxxxx/

 drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c  | 9 ++++++++-
 drivers/hid/intel-thc-hid/intel-quickspi/quickspi-dev.h  | 1 +
 .../hid/intel-thc-hid/intel-quickspi/quickspi-protocol.c | 3 +++
 3 files changed, 12 insertions(+), 1 deletion(-)

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..da5ecfcd0fbf 100644
--- a/drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c
+++ b/drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c
@@ -555,7 +555,14 @@ static int quickspi_alloc_report_buf(struct quickspi_device *qsdev)
 	max_report_len = max(le16_to_cpu(qsdev->dev_desc.max_output_len),
 			     le16_to_cpu(qsdev->dev_desc.max_input_len));
 
-	qsdev->report_buf = devm_kzalloc(qsdev->dev, max_report_len, GFP_KERNEL);
+	/*
+	 * write_cmd_to_txdma() writes the output report header ahead of the
+	 * content in this buffer, so it has to hold both.
+	 */
+	qsdev->report_buf_size = HIDSPI_OUTPUT_REPORT_SIZE(max_report_len);
+
+	qsdev->report_buf = devm_kzalloc(qsdev->dev, qsdev->report_buf_size,
+					 GFP_KERNEL);
 	if (!qsdev->report_buf)
 		return -ENOMEM;
 
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