Revert "firmware_loader: use kernel credentials when reading firmware"

This reverts commit 3677563eb8 as it leaks
memory :(

Reported-by: Qian Cai <quic_qiancai@quicinc.com>
Link: https://lore.kernel.org/r/20220427135823.GD71@qian
Cc: Thiébaud Weksteen <tweek@google.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: John Stultz <jstultz@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/firmware_loader/main.c

@@ -798,8 +798,6 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
 		  size_t offset, u32 opt_flags)
 {
 	struct firmware *fw = NULL;
-	struct cred *kern_cred = NULL;
-	const struct cred *old_cred;
 	bool nondirect = false;
 	int ret;
 
@@ -816,18 +814,6 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
 	if (ret <= 0) /* error or already assigned */
 		goto out;
 
-	/*
-	 * We are about to try to access the firmware file. Because we may have been
-	 * called by a driver when serving an unrelated request from userland, we use
-	 * the kernel credentials to read the file.
-	 */
-	kern_cred = prepare_kernel_cred(NULL);
-	if (!kern_cred) {
-		ret = -ENOMEM;
-		goto out;
-	}
-	old_cred = override_creds(kern_cred);
-
 	ret = fw_get_filesystem_firmware(device, fw->priv, "", NULL);
 
 	/* Only full reads can support decompression, platform, and sysfs. */
@@ -858,8 +844,6 @@ _request_firmware(const struct firmware **firmware_p, const char *name,
 	} else
 		ret = assign_fw(fw, device);
 
-	revert_creds(old_cred);
-
  out:
 	if (ret < 0) {
 		fw_abort_batch_reqs(fw);