HID: core: Correctly handle ReportSize being zero

commit bce1305c0ece3dc549663605e567655dd701752c upstream.

It appears that a ReportSize value of zero is legal, even if a bit
non-sensical. Most of the HID code seems to handle that gracefully,
except when computing the total size in bytes. When fed as input to
memset, this leads to some funky outcomes.

Detect the corner case and correctly compute the size.

Cc: stable@vger.kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 75b0a337114df48220fdb66710394eeca16ed493..ff6e327cbd0275bab65f4656c7085f4cd4969011 100644 (file)
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1426,6 +1426,17 @@ static void hid_output_field(const struct hid_device *hid,
        }
 }
 
+/*
+ * Compute the size of a report.
+ */
+static size_t hid_compute_report_size(struct hid_report *report)
+{
+       if (report->size)
+               return ((report->size - 1) >> 3) + 1;
+
+       return 0;
+}
+
 /*
  * Create a report. 'data' has to be allocated using
  * hid_alloc_report_buf() so that it has proper size.
@@ -1438,7 +1449,7 @@ void hid_output_report(struct hid_report *report, __u8 *data)
        if (report->id > 0)
                *data++ = report->id;
 
-       memset(data, 0, ((report->size - 1) >> 3) + 1);
+       memset(data, 0, hid_compute_report_size(report));
        for (n = 0; n < report->maxfield; n++)
                hid_output_field(report->device, report->field[n], data);
 }
@@ -1565,7 +1576,7 @@ int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,
                csize--;
        }
 
-       rsize = ((report->size - 1) >> 3) + 1;
+       rsize = hid_compute_report_size(report);
 
        if (report_enum->numbered && rsize >= HID_MAX_BUFFER_SIZE)
                rsize = HID_MAX_BUFFER_SIZE - 1;