linux-kernel - [PATCH 4.19 45/87] HID: core: fix off-by-one memset in hid_report_raw

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Date:   Tue,  3 Mar 2020 18:43:36 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Johan Korsnes <jkorsnes@...co.com>,
        Armando Visconti <armando.visconti@...com>,
        Jiri Kosina <jkosina@...e.cz>,
        Alan Stern <stern@...land.harvard.edu>
Subject: [PATCH 4.19 45/87] HID: core: fix off-by-one memset in hid_report_raw_event()

From: Johan Korsnes <jkorsnes@...co.com>

commit 5ebdffd25098898aff1249ae2f7dbfddd76d8f8f upstream.

In case a report is greater than HID_MAX_BUFFER_SIZE, it is truncated,
but the report-number byte is not correctly handled. This results in a
off-by-one in the following memset, causing a kernel Oops and ensuing
system crash.

Note: With commit 8ec321e96e05 ("HID: Fix slab-out-of-bounds read in
hid_field_extract") I no longer hit the kernel Oops as we instead fail
"controlled" at probe if there is a report too long in the HID
report-descriptor. hid_report_raw_event() is an exported symbol, so
presumabely we cannot always rely on this being the case.

Fixes: 966922f26c7f ("HID: fix a crash in hid_report_raw_event()
                     function.")
Signed-off-by: Johan Korsnes <jkorsnes@...co.com>
Cc: Armando Visconti <armando.visconti@...com>
Cc: Jiri Kosina <jkosina@...e.cz>
Cc: Alan Stern <stern@...land.harvard.edu>
Signed-off-by: Jiri Kosina <jkosina@...e.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/hid/hid-core.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1566,7 +1566,9 @@ int hid_report_raw_event(struct hid_devi

 	rsize = ((report->size - 1) >> 3) + 1;

-	if (rsize > HID_MAX_BUFFER_SIZE)
+	if (report_enum->numbered && rsize >= HID_MAX_BUFFER_SIZE)
+		rsize = HID_MAX_BUFFER_SIZE - 1;
+	else if (rsize > HID_MAX_BUFFER_SIZE)
 		rsize = HID_MAX_BUFFER_SIZE;

 	if (csize < rsize) {