Merge tag 'at24-4.15-fixes-for-wolfram' of git://git.kernel.org/pub/scm/linux/kernel/git/brgl/linux into i2c/for-current

Please consider pulling the following fixes for v4.15. While it doesn't
fix any regression introduced in the v4.15 merge window, we have a
feature in at24 since linux v4.8 - reading the mac address block from
at24mac series - which turned out to be not working.

This pull request contains changes that fix it together with a patch
that hardens the read and write argument sanitization with
out-of-bounds checks that were missing.

1 files changed, 18 insertions, 1 deletions

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index e0b4b36ef010..305a7a464d09 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -425,7 +425,8 @@ static ssize_t at24_eeprom_read_mac(struct at24_data *at24, char *buf,
         memset(msg, 0, sizeof(msg));
         msg[0].addr = client->addr;
         msg[0].buf = addrbuf;
-        addrbuf[0] = 0x90 + offset;
+        /* EUI-48 starts from 0x9a, EUI-64 from 0x98 */
+        addrbuf[0] = 0xa0 - at24->chip.byte_len + offset;
         msg[0].len = 1;
         msg[1].addr = client->addr;
         msg[1].flags = I2C_M_RD;
@@ -568,6 +569,9 @@ static int at24_read(void *priv, unsigned int off, void *val, size_t count)
         if (unlikely(!count))
                 return count;
 
+        if (off + count > at24->chip.byte_len)
+                return -EINVAL;
+
         client = at24_translate_offset(at24, &off);
 
         ret = pm_runtime_get_sync(&client->dev);
@@ -613,6 +617,9 @@ static int at24_write(void *priv, unsigned int off, void *val, size_t count)
         if (unlikely(!count))
                 return -EINVAL;
 
+        if (off + count > at24->chip.byte_len)
+                return -EINVAL;
+
         client = at24_translate_offset(at24, &off);
 
         ret = pm_runtime_get_sync(&client->dev);
@@ -730,6 +737,16 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
                 dev_warn(&client->dev,
                         "page_size looks suspicious (no power of 2)!\n");
 
+        /*
+         * REVISIT: the size of the EUI-48 byte array is 6 in at24mac402, while
+         * the call to ilog2() in AT24_DEVICE_MAGIC() rounds it down to 4.
+         *
+         * Eventually we'll get rid of the magic values altoghether in favor of
+         * real structs, but for now just manually set the right size.
+         */
+        if (chip.flags & AT24_FLAG_MAC && chip.byte_len == 4)
+                chip.byte_len = 6;
+
         /* Use I2C operations unless we're stuck with SMBus extensions. */
         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
                 if (chip.flags & AT24_FLAG_ADDR16)