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    Subject[PATCH 5.10 341/545] HID: mcp2221: prevent a buffer overflow in mcp_smbus_write()
    Date
    From: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>

    [ Upstream commit 62ac2473553a00229e67bdf3cb023b62cf7f5a9a ]

    Smatch Warning:
    drivers/hid/hid-mcp2221.c:388 mcp_smbus_write() error: __memcpy()
    '&mcp->txbuf[5]' too small (59 vs 255)
    drivers/hid/hid-mcp2221.c:388 mcp_smbus_write() error: __memcpy() 'buf'
    too small (34 vs 255)

    The 'len' variable can take a value between 0-255 as it can come from
    data->block[0] and it is user data. So add an bound check to prevent a
    buffer overflow in memcpy().

    Fixes: 67a95c21463d ("HID: mcp2221: add usb to i2c-smbus host bridge")
    Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>
    Signed-off-by: Jiri Kosina <jkosina@suse.cz>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/hid/hid-mcp2221.c | 3 +++
    1 file changed, 3 insertions(+)

    diff --git a/drivers/hid/hid-mcp2221.c b/drivers/hid/hid-mcp2221.c
    index 4211b9839209..de52e9f7bb8c 100644
    --- a/drivers/hid/hid-mcp2221.c
    +++ b/drivers/hid/hid-mcp2221.c
    @@ -385,6 +385,9 @@ static int mcp_smbus_write(struct mcp2221 *mcp, u16 addr,
    data_len = 7;
    break;
    default:
    + if (len > I2C_SMBUS_BLOCK_MAX)
    + return -EINVAL;
    +
    memcpy(&mcp->txbuf[5], buf, len);
    data_len = len + 5;
    }
    --
    2.35.1


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