From: <Alexander.Steffen-d0qZbvYSIPpWk0Htik3Jemail@example.com> To: jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcnfirstname.lastname@example.org Cc: tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Subject: Re: [PATCH 1/3] tpm-chip: Move idr_replace calls to appropriate places Date: Thu, 27 Jul 2017 14:07:49 +0000 [thread overview] Message-ID: <016fe4c80f0c4b209ac2337500f9dd2b@MUCSE603.infineon.com> (raw) In-Reply-To: <20170709212430.GB19327-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcnemail@example.com> > > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c > > index 67ec9d3..a353b7a 100644 > > +++ b/drivers/char/tpm/tpm-chip.c > > @@ -327,11 +327,6 @@ static int tpm_add_char_device(struct tpm_chip > *chip) > > } > > } > > > > - /* Make the chip available. */ > > - mutex_lock(&idr_lock); > > - idr_replace(&dev_nums_idr, chip, chip->dev_num); > > - mutex_unlock(&idr_lock); > > This is actually in the wrong place already, it needs to be done before > cdev_device_add - this is because cdev_device_add generates the uevent to > userspace which could trigger userspace to use the kernel device. So a patch > to move it to the start of this function woud be good. The function would be > better described as 'make visible' I have looked again at the code and I am not sure this is an issue. The call to idr_replace is only necessary to enable in-kernel usage (i.e. RNG, IMA, ...) of the TPM, but it should not affect userspace in any way. So the location of the idr_replace call does not matter much, as long as the TPM is already initialized. In fact, the main purpose of this patch series (please see PATCH 3/3) is to export the device to userspace without calling idr_replace at all under some circumstances. Or is there something I missed? The only function that ever tries to access the value stored by idr_replace is tpm_chip_find_get. It is usually called with TPM_ANY_NUM, selecting any TPM that might be present. If no TPM is present (or if idr_replace has not been called) the caller needs to deal with the situation already. Alexander ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
prev parent reply other threads:[~2017-07-27 14:07 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-07-04 13:56 Alexander Steffen [not found] ` <20170704135648.7360-1-Alexander.Steffen-d0qZbvYSIPpWk0Htik3Jfirstname.lastname@example.org> 2017-07-04 13:56 ` [PATCH 2/3] tpm-chip: Return TPM error codes from auto_startup functions Alexander Steffen 2017-07-04 13:56 ` [PATCH 3/3] tpm-chip: Export TPM device to user space even when startup failed Alexander Steffen 2017-07-09 21:24 ` [PATCH 1/3] tpm-chip: Move idr_replace calls to appropriate places Jason Gunthorpe [not found] ` <20170709212430.GB19327-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcnemail@example.com> 2017-07-27 14:07 ` Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w [this message]
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