From 5ebdffd25098898aff1249ae2f7dbfddd76d8f8f Mon Sep 17 00:00:00 2001
From: Johan Korsnes <jkorsnes@cisco.com>
Date: Fri, 17 Jan 2020 13:08:35 +0100
Subject: [PATCH] HID: core: fix off-by-one memset in hid_report_raw_event()
Git-commit: 5ebdffd25098898aff1249ae2f7dbfddd76d8f8f
Patch-mainline: v5.6-rc4
References: bsc#1051510

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@cisco.com>
Cc: Armando Visconti <armando.visconti@st.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Acked-by: Takashi Iwai <tiwai@suse.de>

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

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 851fe54ea59e..359616e3efbb 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1741,7 +1741,9 @@ int hid_report_raw_event(struct hid_device *hid, int type, u8 *data, u32 size,
 
 	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) {
-- 
2.16.4