From: Marc Zyngier maz@kernel.org

stable inclusion from linux-4.19.144 commit abae259fdccc5e41ff302dd80a2b944ce385c970 CVE: CVE-2020-0465

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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 Signed-off-by: Yang Yingliang yangyingliang@huawei.com Reviewed-by: Jason Yan yanaijie@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- drivers/hid/hid-core.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index 3a359716fb38..3178580db7fa 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -1419,6 +1419,17 @@ 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. @@ -1431,7 +1442,7 @@ 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); } @@ -1558,7 +1569,7 @@ 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 (rsize > HID_MAX_BUFFER_SIZE) rsize = HID_MAX_BUFFER_SIZE;