eeprom: at24: fix memory corruption race condition

If the eeprom is not accessible, an nvmem device will be registered, the
read will fail, and the device will be torn down. If another driver
accesses the nvmem device after the teardown, it will reference
invalid memory.

Move the failure point before registering the nvmem device.

Signed-off-by: Daniel Okazaki <dtokazaki@google.com>
Fixes: b20eb4c1f026 ("eeprom: at24: drop unnecessary label")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240422174337.2487142-1-dtokazaki@google.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 572333ead5fb8b002b87957dfe1dc9ea26330efb..4bd4f32bcdabb8f98d2b764f04bb2ac9f8270d83 100644 (file)
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -758,15 +758,6 @@ static int at24_probe(struct i2c_client *client)
        }
        pm_runtime_enable(dev);
 
-       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
-       if (IS_ERR(at24->nvmem)) {
-               pm_runtime_disable(dev);
-               if (!pm_runtime_status_suspended(dev))
-                       regulator_disable(at24->vcc_reg);
-               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
-                                    "failed to register nvmem\n");
-       }
-
        /*
         * Perform a one-byte test read to verify that the chip is functional,
         * unless powering on the device is to be avoided during probe (i.e.
@@ -782,6 +773,15 @@ static int at24_probe(struct i2c_client *client)
                }
        }
 
+       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
+       if (IS_ERR(at24->nvmem)) {
+               pm_runtime_disable(dev);
+               if (!pm_runtime_status_suspended(dev))
+                       regulator_disable(at24->vcc_reg);
+               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
+                                    "failed to register nvmem\n");
+       }
+
        /* If this a SPD EEPROM, probe for DDR3 thermal sensor */
        if (cdata == &at24_data_spd)
                at24_probe_temp_sensor(client);