eeprom: at24: check at24_read/write arguments

BugLink: http://bugs.launchpad.net/bugs/1745043

commit d9bcd462 upstream.

So far we completely rely on the caller to provide valid arguments.
To be on the safe side perform an own sanity check.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/misc/eeprom/at24.c

@@ -257,6 +257,9 @@ static ssize_t at24_read(struct at24_data *at24,
 	if (unlikely(!count))
 		return count;
 
+	if (off + count > at24->chip.byte_len)
+		return -EINVAL;
+
 	/*
 	 * Read data from chip, protecting against concurrent updates
 	 * from this host, but not from other I2C masters.
@@ -311,6 +314,9 @@ static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
 	unsigned long timeout, write_time;
 	unsigned next_page;
 
+	if (offset + count > at24->chip.byte_len)
+		return -EINVAL;
+
 	/* Get corresponding I2C address and adjust offset */
 	client = at24_translate_offset(at24, &offset);