[PATCH] HID: i2c-hid: fix OOB write in i2c_hid_set_or_send_report()

[Dmitry Torokhov]

From: Dmitry Torokhov <dtor@xxxxxxxxxxxx>

Even though hid_hw_* checks that passed in data_len is less than
HID_MAX_BUFFER_SIZE it is not enough, as i2c-hid does not necessarily
allocate buffers of HID_MAX_BUFFER_SIZE but rather checks all device
reports and select largest size. In-kernel users normally just send as much
data as report needs, so there is no problem, but hidraw users can do
whatever they please:

BUG: KASAN: slab-out-of-bounds in memcpy+0x34/0x54 at addr ffffffc07135ea80
Write of size 4101 by task syz-executor/8747
CPU: 2 PID: 8747 Comm: syz-executor Tainted: G    BU         3.18.0 #37
Hardware name: Google Tegra210 Smaug Rev 1,3+ (DT)
Call trace:
[<ffffffc00020ebcc>] dump_backtrace+0x0/0x258 arch/arm64/kernel/traps.c:83
[<ffffffc00020ee40>] show_stack+0x1c/0x2c arch/arm64/kernel/traps.c:172
[<     inline     >] __dump_stack lib/dump_stack.c:15
[<ffffffc001958114>] dump_stack+0x90/0x140 lib/dump_stack.c:50
[<     inline     >] print_error_description mm/kasan/report.c:97
[<     inline     >] kasan_report_error mm/kasan/report.c:278
[<ffffffc0004597dc>] kasan_report+0x268/0x530 mm/kasan/report.c:305
[<ffffffc0004592e8>] __asan_storeN+0x20/0x150 mm/kasan/kasan.c:718
[<ffffffc0004594e0>] memcpy+0x30/0x54 mm/kasan/kasan.c:299
[<ffffffc001306354>] __i2c_hid_command+0x2b0/0x7b4 drivers/hid/i2c-hid/i2c-hid.c:178
[<     inline     >] i2c_hid_set_or_send_report drivers/hid/i2c-hid/i2c-hid.c:321
[<ffffffc0013079a0>] i2c_hid_output_raw_report.isra.2+0x3d4/0x4b8 drivers/hid/i2c-hid/i2c-hid.c:589
[<ffffffc001307ad8>] i2c_hid_output_report+0x54/0x68 drivers/hid/i2c-hid/i2c-hid.c:602
[<     inline     >] hid_hw_output_report include/linux/hid.h:1039
[<ffffffc0012cc7a0>] hidraw_send_report+0x400/0x414 drivers/hid/hidraw.c:154
[<ffffffc0012cc7f4>] hidraw_write+0x40/0x64 drivers/hid/hidraw.c:177
[<ffffffc0004681dc>] vfs_write+0x1d4/0x3cc fs/read_write.c:534
[<     inline     >] SYSC_pwrite64 fs/read_write.c:627
[<ffffffc000468984>] SyS_pwrite64+0xec/0x144 fs/read_write.c:614
Object at ffffffc07135ea80, in cache kmalloc-512
Object allocated with size 268 bytes.

Let's check data length against the buffer size before attempting to copy
data over.

Reported-by: Alexander Potapenko <glider@xxxxxxxxxx>
Signed-off-by: Dmitry Torokhov <dtor@xxxxxxxxxxxx>
---

This should probably go to stable as well, leaving it to Jiri/Benjamin
to decide.


 drivers/hid/i2c-hid/i2c-hid.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
index b921693..bb89749 100644
--- a/drivers/hid/i2c-hid/i2c-hid.c
+++ b/drivers/hid/i2c-hid/i2c-hid.c
@@ -283,17 +283,21 @@ static int i2c_hid_set_or_send_report(struct i2c_client *client, u8 reportType,
 	u16 dataRegister = le16_to_cpu(ihid->hdesc.wDataRegister);
 	u16 outputRegister = le16_to_cpu(ihid->hdesc.wOutputRegister);
 	u16 maxOutputLength = le16_to_cpu(ihid->hdesc.wMaxOutputLength);
+	u16 size;
+	int args_len;
+	int index = 0;
+
+	i2c_hid_dbg(ihid, "%s\n", __func__);
+
+	if (data_len > ihid->bufsize)
+		return -EINVAL;
 
-	/* hid_hw_* already checked that data_len < HID_MAX_BUFFER_SIZE */
-	u16 size =	2			/* size */ +
+	size =		2			/* size */ +
 			(reportID ? 1 : 0)	/* reportID */ +
 			data_len		/* buf */;
-	int args_len =	(reportID >= 0x0F ? 1 : 0) /* optional third byte */ +
+	args_len =	(reportID >= 0x0F ? 1 : 0) /* optional third byte */ +
 			2			/* dataRegister */ +
 			size			/* args */;
-	int index = 0;
-
-	i2c_hid_dbg(ihid, "%s\n", __func__);
 
 	if (!use_data && maxOutputLength == 0)
 		return -ENOSYS;
-- 
2.7.0.rc3.207.g0ac5344


-- 
Dmitry