char: tpm: Fix possible memory leak in tpm_bios_measurements_open()

BugLink: https://bugs.launchpad.net/bugs/2078388

commit 5d8e2971e817bb64225fc0b6327a78752f58a9aa upstream.

In tpm_bios_measurements_open(), get_device() is called on the device
embedded in struct tpm_chip. In the error path, however, put_device() is
not called. This results in a reference count leak, which prevents the
device from being properly released. This commit makes sure to call
put_device() when the seq_open() call fails.

Cc: stable@vger.kernel.org # +v4.18
Fixes: 9b01b53566 ("tpm: Move shared eventlog functions to common.c")
Signed-off-by: Joe Hattori <joe@pf.is.s.u-tokyo.ac.jp>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/char/tpm/eventlog/common.c

@@ -47,6 +47,8 @@ static int tpm_bios_measurements_open(struct inode *inode,
 	if (!err) {
 		seq = file->private_data;
 		seq->private = chip;
+	} else {
+		put_device(&chip->dev);
 	}
 
 	return err;