Setting TPM_CHIP_FLAG_SUSPENDED in the end of tpm_pm_suspend() can be racy
according, as this leaves window for tpm_hwrng_read() to be called while
the operation is in progress. The recent bug report gives also evidence of
this behaviour.
Aadress this by locking the TPM chip before checking any chip->flags both
in tpm_pm_suspend() and tpm_hwrng_read(). Move TPM_CHIP_FLAG_SUSPENDED
check inside tpm_get_random() so that it will be always checked only when
the lock is reserved.
Cc: stable@vger.kernel.org # v6.4+
Fixes: 99d4645062 ("tpm: Prevent hwrng from activating during resume")
Reported-by: Mike Seo <mikeseohyungjin@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219383
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Tested-by: Mike Seo <mikeseohyungjin@gmail.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
9265fed6db