6.15-stable review patch. If anyone has any objections, please let me know.
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From: Benjamin Tissoires bentiss@kernel.org
commit 0d0777ccaa2d46609d05b66ba0096802a2746193 upstream.
The low level transport driver expects the first byte to be the report ID, even when the report ID is not use (in which case they just shift the buffer).
However, __hid_request() whas not offsetting the buffer it used by one in this case, meaning that the raw_request() callback emitted by the transport driver would be stripped of the first byte.
Note: this changes the API for uhid devices when a request is made through hid_hw_request. However, several considerations makes me think this is fine: - every request to a HID device made through hid_hw_request() would see that change, but every request made through hid_hw_raw_request() already has the new behaviour. So that means that the users are already facing situations where they might have or not the first byte being the null report ID when it is 0. We are making things more straightforward in the end. - uhid is mainly used for BLE devices - uhid is also used for testing, but I don't see that change a big issue - for BLE devices, we can check which kernel module is calling hid_hw_request() - and in those modules, we can check which are using a Bluetooth device - and then we can check if the command is used with a report ID or not. - surprise: none of the kernel module are using a report ID 0 - and finally, bluez, in its function set_report()[0], does the same shift if the report ID is 0 and the given buffer has a size > 0.
[0] https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/profiles/input/hog-l...
Reported-by: Alan Stern stern@rowland.harvard.edu Closes: https://lore.kernel.org/linux-input/c75433e0-9b47-4072-bbe8-b1d14ea97b13@row... Reported-by: syzbot+8258d5439c49d4c35f43@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=8258d5439c49d4c35f43 Tested-by: syzbot+8258d5439c49d4c35f43@syzkaller.appspotmail.com Fixes: 4fa5a7f76cc7 ("HID: core: implement generic .request()") Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20250710-report-size-null-v2-2-ccf922b7c4e5@kernel.... Signed-off-by: Benjamin Tissoires bentiss@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/hid/hid-core.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
--- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -1976,7 +1976,7 @@ static struct hid_report *hid_get_report int __hid_request(struct hid_device *hid, struct hid_report *report, enum hid_class_request reqtype) { - char *buf; + char *buf, *data_buf; int ret; u32 len;
@@ -1984,10 +1984,17 @@ int __hid_request(struct hid_device *hid if (!buf) return -ENOMEM;
+ data_buf = buf; len = hid_report_len(report);
+ if (report->id == 0) { + /* reserve the first byte for the report ID */ + data_buf++; + len++; + } + if (reqtype == HID_REQ_SET_REPORT) - hid_output_report(report, buf); + hid_output_report(report, data_buf);
ret = hid->ll_driver->raw_request(hid, report->id, buf, len, report->type, reqtype);