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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Johan Korsnes <jkorsnes@cisco.com>,
        Armando Visconti <armando.visconti@st.com>,
        Jiri Kosina <jkosina@suse.cz>,
        Alan Stern <stern@rowland.harvard.edu>
Subject: [PATCH 5.5 091/176] HID: core: fix off-by-one memset in hid_report_raw_event()
Date:   Tue,  3 Mar 2020 18:42:35 +0100
Message-Id: <20200303174315.347608869@linuxfoundation.org>
In-Reply-To: <20200303174304.593872177@linuxfoundation.org>
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From: Johan Korsnes <jkorsnes@cisco.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@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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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
@@ -1741,7 +1741,9 @@ 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) {