From 28dc683fa2af83ec36749b17578f7a6c42c9e374 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Sat, 29 Aug 2020 12:26:01 +0100 Subject: [PATCH] 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. Mot-CRs-fixed: (CR) CVE-Fixed: CVE-2020-0465 Bug: 162844689 Cc: stable@vger.kernel.org Signed-off-by: Marc Zyngier Signed-off-by: Benjamin Tissoires Signed-off-by: Greg Kroah-Hartman Signed-off-by: Lee Jones Change-Id: I0e61ea8b763669affdff3b8788a5fc66a8b7fcd3 Signed-off-by: Jignesh Patel Reviewed-on: https://gerrit.mot.com/1796757 SLTApproved: Slta Waiver SME-Granted: SME Approvals Granted Tested-by: Jira Key Reviewed-by: Xiangpo Zhao Submit-Approved: Jira Key --- 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 a306493e2e97..350f6fa04d0f 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -1362,6 +1362,17 @@ 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. @@ -1374,7 +1385,7 @@ 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); } @@ -1501,7 +1512,7 @@ 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; -- 2.20.1