From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A19D91E9919; Tue, 11 Aug 2026 00:03:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786406628; cv=none; b=eMohvY0kVtVwHARlL3vvGjNfEK3ga7Mt2lW1KA+MzJ8tsKmgeZZWOzwKrDkRKUyi0gizHnzNxPwxKHx8KnWtJ0RrYllonyIqVCcrALTu0YPTv6fksBObF+VJu/DgzaiCpEPdJ8CiXI38EM70P1ZMjjMrS8v4YMUuqlb5raDD8w4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786406628; c=relaxed/simple; bh=/P9QHm2zHqotMSSe2iZuuUACd1GyWWvR5GnC/hFwLpU=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=b2zDbwBX7GEf2SXKqrecoWcqMoutoqLW9NTrh3Sduc5kBtJq5QeUvUeCeZ7YjSxKjLCDNGT/kOzf5Pfmrn4ULR9IAU8GXZw+dhO+p5DLVZjmvDj9sxN1+8CiuXOtwWr/LZyYDCg9oJiUeOU9/qvkBrZRJttK3vyLckXqeUMNAOU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AdpWzzYs; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AdpWzzYs" Received: by smtp.kernel.org (Postfix) with UTF8SMTPSA id 2EF3A1F000E9; Tue, 11 Aug 2026 00:03:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786406621; bh=mtkm9rvDeXZtH8T6a3Zip6v46uf5BfM9kAQfKxkAkfA=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=AdpWzzYszYIHkD4M/HyZOvoFXbjQw2VKhMGjZezswGolK23+xVO8IAPvJ7orsaLrR eGiIgv2FDAUuHW9pfZ4qMmGQmuYA5aqE3vOhGg8CthItizILNBG/OyReAz2LPRqdmj z52EA0TlqZ3pckqwpphzOEdG40sZ/vinSn3kTcIAmcMGTYHPqQ6dZsGUh9AN3iiG/E 8bM8cAIHE1W1qA/FwdT/9P/Zg04d4CANyU9SFV8Uwe6Fy+1dYKefGRbZ24c+wd2S8/ N8NsCmeYuWBeBOe95Tovle5Y5pArn+SPWmkpFhFm6EignfYy/QO+JcDSX3RQmkAsvM YUoH5iEkMTzTA== Date: Tue, 11 Aug 2026 03:03:37 +0300 From: Jarkko Sakkinen To: Thomas Fourier Cc: stable@vger.kernel.org, Peter Huewe , Jason Gunthorpe , Jerry Snitselaar , "open list:TPM DEVICE DRIVER" , open list Subject: Re: [PATCH] tpm: Fix barriers to prevent hwrng from activating during resume Message-ID: References: <20260803092240.18348-2-fourier.thomas@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260803092240.18348-2-fourier.thomas@gmail.com> On Mon, Aug 03, 2026 at 11:13:24AM +0200, Thomas Fourier wrote: > The memory barrier is placed after clearing the suspened flag so > memory reordering between the wake up and clearing the flag is allowed. > The reader of the flag is missing the corresponding barrier. > > Clear the flag after the memory barrier and add a memory barrier in > the reader. > > Fixes: 99d464506255 ("tpm: Prevent hwrng from activating during resume") > Cc: > Signed-off-by: Thomas Fourier > --- I tagged this too quickly, sorry, let's revisit the patch a bit just to make sure that we do right things right. > drivers/char/tpm/tpm-chip.c | 3 +++ > drivers/char/tpm/tpm-interface.c | 3 +-- > 2 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c > index 12b7394b34bd..7f500797b7a7 100644 > --- a/drivers/char/tpm/tpm-chip.c > +++ b/drivers/char/tpm/tpm-chip.c > @@ -173,6 +173,9 @@ int tpm_try_get_ops(struct tpm_chip *chip) > if (chip->flags & TPM_CHIP_FLAG_SUSPENDED) > goto out_lock; > > + /* Ensure that device is fully resumed */ > + rmb(); > + > rc = tpm_chip_start(chip); > if (rc) > goto out_lock; > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c > index f745a098908b..2de12b02f62b 100644 > --- a/drivers/char/tpm/tpm-interface.c > +++ b/drivers/char/tpm/tpm-interface.c > @@ -474,13 +474,12 @@ int tpm_pm_resume(struct device *dev) > if (chip == NULL) > return -ENODEV; > > - chip->flags &= ~TPM_CHIP_FLAG_SUSPENDED; > - > /* > * Guarantee that SUSPENDED is written last, so that hwrng does not > * activate before the chip has been fully resumed. > */ > wmb(); > + chip->flags &= ~TPM_CHIP_FLAG_SUSPENDED; Can you rationalize this change? > > return 0; > } > -- > 2.43.0 > BR, Jarkko