From 55a9d836785698b04bf9d2acc086b34412dbdf82 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Mon, 18 Jan 2021 10:51:23 +0800 Subject: [PATCH] HID: core: Correctly handle ReportSize being zero stable inclusion from linux-4.19.144 commit abae259fdccc5e41ff302dd80a2b944ce385c970 CVE: CVE-2020-0465 -------------------------------- 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 Signed-off-by: Benjamin Tissoires Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yang Yingliang Reviewed-by: Jason Yan Signed-off-by: Yang Yingliang --- 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 2c85d075daee..05122167d9d8 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -1425,6 +1425,17 @@ 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. @@ -1437,7 +1448,7 @@ 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); } @@ -1564,7 +1575,7 @@ 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; -- GitLab