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Subject[PATCH AUTOSEL 4.19 03/31] HID: core: fix off-by-one memset in hid_report_raw_event()
Date
From: Johan Korsnes <jkorsnes@cisco.com>

[ Upstream commit 5ebdffd25098898aff1249ae2f7dbfddd76d8f8f ]

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: Sasha Levin <sashal@kernel.org>
---
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 e723156057a64..2c85d075daee1 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1566,7 +1566,9 @@ 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) {
--
2.20.1
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