nvmem: u-boot-env: error if NVMEM device is too small

Verify data size before trying to parse it to avoid reading out of
buffer. This could happen in case of problems at MTD level or invalid DT
bindings.

Signed-off-by: John Thomson <git@johnthomson.fastmail.com.au>
Cc: stable <stable@kernel.org>
Fixes: d554292 ("nvmem: add driver handling U-Boot environment variables")
[rmilecki: simplify commit description & rebase]
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20240902142510.71096-2-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: john-tho

drivers/nvmem/u-boot-env.c

@@ -176,6 +176,13 @@ static int u_boot_env_parse(struct u_boot_env *priv)
 		data_offset = offsetof(struct u_boot_env_image_broadcom, data);
 		break;
 	}
+
+	if (dev_size < data_offset) {
+		dev_err(dev, "Device too small for u-boot-env\n");
+		err = -EIO;
+		goto err_kfree;
+	}
+
 	crc32_addr = (__le32 *)(buf + crc32_offset);
 	crc32 = le32_to_cpu(*crc32_addr);
 	crc32_data_len = dev_size - crc32_data_offset;