linux-kernel - Re: [PATCH] tpm: Revert "tpm: fix invalid locking in NONBLOCKING mode"

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Date:   Tue, 26 May 2020 16:06:10 -0700
From:   James Bottomley <James.Bottomley@...senPartnership.com>
To:     Alex Guzman <alex@...man.io>, Mario.Limonciello@...l.com,
        peterhuewe@....de, jarkko.sakkinen@...ux.intel.com, jgg@...pe.ca
Cc:     arnd@...db.de, gregkh@...uxfoundation.org,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        jeffrin@...agiritech.edu.in
Subject: Re: [PATCH] tpm: Revert "tpm: fix invalid locking in NONBLOCKING
 mode"

On Tue, 2020-05-26 at 15:19 -0700, Alex Guzman wrote:
[...]
> When using your patch, I get a hang when trying to use tpm2_getcap,
> and dmesg shows some info.

Are you sure it's all applied?  This

> [  570.913803]  tpm_tcg_write_bytes+0x2f/0x40
> [  570.913805]  release_locality+0x49/0x220
> [  570.913807]  tpm_relinquish_locality+0x1f/0x40
> [  570.913808]  tpm_chip_stop+0x21/0x40
> [  570.913810]  tpm_put_ops+0x9/0x30
> [  570.913811]  tpm_common_write+0x179/0x190
> [  570.913813]  vfs_write+0xb1/0x1a0

Implies an unmatched tpm_put_ops() in the async write path, as though
this hunk:

> @@ -211,11 +202,19 @@ ssize_t tpm_common_write(struct file *file,
> const char __user *buf,
>         if (file->f_flags & O_NONBLOCK) {
>                 priv->command_enqueued = true;
>                 queue_work(tpm_dev_wq, &priv->async_work);
> -               tpm_put_ops(priv->chip);
>                 mutex_unlock(&priv->buffer_mutex);
>                 return size;
>         }

Is missing.  I actually booted the patch in my TPM based VM and it all
seems to work OK when I execute tpm2_getcap (I verified it's using
O_NONBLOCK) and tssgetcapability in sync mode.

James