Re: [PATCH v5 4/7] tpm: fix the race condition between event log access and chip getting unregistered

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Tue, Oct 18, 2016 at 08:49:42PM -0400, Nayna Jain wrote:
> +	struct tpm_chip_seqops *chip_seqops;
> +	const struct seq_operations *seqops;
> +	struct tpm_chip *chip;
> +
> +	inode_lock(inode);
> +	if (!inode->i_private) {
> +		inode_unlock(inode);
> +		return -ENODEV;
> +	}
> +	chip_seqops = (struct tpm_chip_seqops *)inode->i_private;
> +	seqops = chip_seqops->seqops;
> +	chip = chip_seqops->chip;
> +	get_device(&chip->dev);

The inode_unlock should be here, not further below - reduces the risk of
deadlocking.

> +	rc = read_log(chip);
> +	/*
> +	 * read_log failure means event log is not supported except for ENOMEM
> +	 */
> +	if (rc < 0) {
> +		if (rc == -ENOMEM)

It would be more consistent to use -ENODEV as indicating no support,
and everything else is pass as an error

Rest looks right to me

Jason

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