[PATCH v4.14.y 1/2] HID: core: Provide new max_buffer_size attribute to over-ride the default

[PATCH v4.14.y 1/2] HID: core: Provide new max_buffer_size attribute to over-ride the default

[Lee Jones]

commit b1a37ed00d7908a991c1d0f18a8cba3c2aa99bdc upstream.

Presently, when a report is processed, its proposed size, provided by
the user of the API (as Report Size * Report Count) is compared against
the subsystem default HID_MAX_BUFFER_SIZE (16k).  However, some
low-level HID drivers allocate a reduced amount of memory to their
buffers (e.g. UHID only allocates UHID_DATA_MAX (4k) buffers), rending
this check inadequate in some cases.

In these circumstances, if the received report ends up being smaller
than the proposed report size, the remainder of the buffer is zeroed.
That is, the space between sizeof(csize) (size of the current report)
and the rsize (size proposed i.e. Report Size * Report Count), which can
be handled up to HID_MAX_BUFFER_SIZE (16k).  Meaning that memset()
shoots straight past the end of the buffer boundary and starts zeroing
out in-use values, often resulting in calamity.

This patch introduces a new variable into 'struct hid_ll_driver' where
individual low-level drivers can over-ride the default maximum value of
HID_MAX_BUFFER_SIZE (16k) with something more sympathetic to the
interface.

Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[Lee: Backported to v4.14.y]
Signed-off-by: Lee Jones <lee@kernel.org>
---
 drivers/hid/hid-core.c | 18 +++++++++++++-----
 include/linux/hid.h    |  3 +++
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index ab78c1e6f37d8..fe3824a6af5c1 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -245,6 +245,7 @@ static int hid_add_field(struct hid_parser *parser, unsigned report_type, unsign
 	unsigned usages;
 	unsigned offset;
 	unsigned i;
+	unsigned int max_buffer_size = HID_MAX_BUFFER_SIZE;
 
 	report = hid_register_report(parser->device, report_type, parser->global.report_id);
 	if (!report) {
@@ -268,8 +269,11 @@ static int hid_add_field(struct hid_parser *parser, unsigned report_type, unsign
 	offset = report->size;
 	report->size += parser->global.report_size * parser->global.report_count;
 
+	if (parser->device->ll_driver->max_buffer_size)
+		max_buffer_size = parser->device->ll_driver->max_buffer_size;
+
 	/* Total size check: Allow for possible report index byte */
-	if (report->size > (HID_MAX_BUFFER_SIZE - 1) << 3) {
+	if (report->size > (max_buffer_size - 1) << 3) {
 		hid_err(parser->device, "report is too long\n");
 		return -1;
 	}
@@ -1568,6 +1572,7 @@ int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,
 	struct hid_report_enum *report_enum = hid->report_enum + type;
 	struct hid_report *report;
 	struct hid_driver *hdrv;
+	int max_buffer_size = HID_MAX_BUFFER_SIZE;
 	unsigned int a;
 	u32 rsize, csize = size;
 	u8 *cdata = data;
@@ -1584,10 +1589,13 @@ int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,
 
 	rsize = hid_compute_report_size(report);
 
-	if (report_enum->numbered && rsize >= HID_MAX_BUFFER_SIZE)
-		rsize = HID_MAX_BUFFER_SIZE - 1;
-	else if (rsize > HID_MAX_BUFFER_SIZE)
-		rsize = HID_MAX_BUFFER_SIZE;
+	if (hid->ll_driver->max_buffer_size)
+		max_buffer_size = hid->ll_driver->max_buffer_size;
+
+	if (report_enum->numbered && rsize >= max_buffer_size)
+		rsize = max_buffer_size - 1;
+	else if (rsize > max_buffer_size)
+		rsize = max_buffer_size;
 
 	if (csize < rsize) {
 		dbg_hid("report %d is too short, (%d < %d)\n", report->id,
diff --git a/include/linux/hid.h b/include/linux/hid.h
index f2a1f34f41e8f..b5fcc8b0b7ce1 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -770,6 +770,7 @@ struct hid_driver {
  * @raw_request: send raw report request to device (e.g. feature report)
  * @output_report: send output report to device
  * @idle: send idle request to device
+ * @max_buffer_size: over-ride maximum data buffer size (default: HID_MAX_BUFFER_SIZE)
  */
 struct hid_ll_driver {
 	int (*start)(struct hid_device *hdev);
@@ -794,6 +795,8 @@ struct hid_ll_driver {
 	int (*output_report) (struct hid_device *hdev, __u8 *buf, size_t len);
 
 	int (*idle)(struct hid_device *hdev, int report, int idle, int reqtype);
+
+	unsigned int max_buffer_size;
 };
 
 extern struct hid_ll_driver i2c_hid_ll_driver;
-- 
2.40.0.rc1.284.g88254d51c5-goog

[PATCH v4.14.y 2/2] HID: uhid: Over-ride the default maximum data buffer value with our own

[Lee Jones]

commit 1c5d4221240a233df2440fe75c881465cdf8da07 upstream.

The default maximum data buffer size for this interface is UHID_DATA_MAX
(4k).  When data buffers are being processed, ensure this value is used
when ensuring the sanity, rather than a value between the user provided
value and HID_MAX_BUFFER_SIZE (16k).

Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Lee Jones <lee@kernel.org>
---
 drivers/hid/uhid.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 333b6a769189c..b7efc5c055be1 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -399,6 +399,7 @@ struct hid_ll_driver uhid_hid_driver = {
 	.parse = uhid_hid_parse,
 	.raw_request = uhid_hid_raw_request,
 	.output_report = uhid_hid_output_report,
+	.max_buffer_size = UHID_DATA_MAX,
 };
 EXPORT_SYMBOL_GPL(uhid_hid_driver);
 
-- 
2.40.0.rc1.284.g88254d51c5-goog