HID: usbhid: fix info leak in hid_submit_ctrl

In hid_submit_ctrl(), the way of calculating the report length doesn't
take into account that report->size can be zero. When running the
syzkaller reproducer, a report of size 0 causes hid_submit_ctrl) to
calculate transfer_buffer_length as 16384. When this urb is passed to
the usb core layer, KMSAN reports an info leak of 16384 bytes.

To fix this, first modify hid_report_len() to account for the zero
report size case by using DIV_ROUND_UP for the division. Then, call it
from hid_submit_ctrl().

Reported-by: syzbot+7c2bb71996f95a82524c@syzkaller.appspotmail.com
Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c
index 86257ce6d61982256648ef36fc511f63205cb519..4e9077363c962c0e5425d698887ada7096cf4731 100644 (file)
--- a/drivers/hid/usbhid/hid-core.c
+++ b/drivers/hid/usbhid/hid-core.c
@@ -374,7 +374,7 @@ static int hid_submit_ctrl(struct hid_device *hid)
        raw_report = usbhid->ctrl[usbhid->ctrltail].raw_report;
        dir = usbhid->ctrl[usbhid->ctrltail].dir;
 
-       len = ((report->size - 1) >> 3) + 1 + (report->id > 0);
+       len = hid_report_len(report);
        if (dir == USB_DIR_OUT) {
                usbhid->urbctrl->pipe = usb_sndctrlpipe(hid_to_usb_dev(hid), 0);
                usbhid->urbctrl->transfer_buffer_length = len;

diff --git a/include/linux/hid.h b/include/linux/hid.h
index 271021e20a3f8d468bd507c7178ae2691a70cabd..10e922cee4ebbd732dad747a739b36e7bf12aa0c 100644 (file)
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -1167,8 +1167,7 @@ static inline void hid_hw_wait(struct hid_device *hdev)
  */
 static inline u32 hid_report_len(struct hid_report *report)
 {
-       /* equivalent to DIV_ROUND_UP(report->size, 8) + !!(report->id > 0) */
-       return ((report->size - 1) >> 3) + 1 + (report->id > 0);
+       return DIV_ROUND_UP(report->size, 8) + (report->id > 0);
 }
 
 int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,