linux-kernel - Re: [PATCH v3] tpm, tpm_crb: fix unaligned read of the command buffer address

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Date:	Wed, 16 Sep 2015 10:19:17 +0300
From:	Jarkko Sakkinen <jarkko.sakkinen@...el.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	Peter Huewe <peterhuewe@....de>,
	Marcel Selhorst <tpmdd@...horst.net>
Subject: Re: [PATCH v3] tpm, tpm_crb: fix unaligned read of the command
 buffer address

On Tue, Sep 15, 2015 at 11:22:27AM -0600, Jason Gunthorpe wrote:
> On Tue, Sep 15, 2015 at 08:05:40PM +0300, Jarkko Sakkinen wrote:
> > The command buffer address must be read with exactly two 32-bit reads.
> > Otherwise, on some HW platforms, it seems that HW will abort the read
> > operation, which causes CPU to fill the read bytes with 1's. Therefore,
> > we cannot rely on memcpy_fromio() but must call ioread32() two times
> > instead.
> > 
> > Also, this matches the PC Client Platform TPM Profile specification,
> > which defines command buffer address with two 32-bit fields.
> > 
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> >  drivers/char/tpm/tpm_crb.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
> > index b4564b6..c09b370 100644
> > +++ b/drivers/char/tpm/tpm_crb.c
> > @@ -68,7 +68,8 @@ struct crb_control_area {
> >  	u32 int_enable;
> >  	u32 int_sts;
> >  	u32 cmd_size;
> > -	u64 cmd_pa;
> > +	u32 cmd_pa_low;
> > +	u32 cmd_pa_high;
> >  	u32 rsp_size;
> >  	u64 rsp_pa;
> 
> What about rsp_pa?

It's naturally aligned and defined as 64-bit field in:

http://www.trustedcomputinggroup.org/developers/pc_client/specifications

Also in a platform (not available in public yet) it gets read correctly.

> >  } __packed;
> 
> As I mentioned, drop the __packed.

I didn't do that because it is not mandatory for the bug fix.

I would rather submit it as a separate commit later on.

> Otherwise:
> 
> Reviewed-By: Jason Gunthorpe <jgunthorpe@...idianresearch.com>
> 
> Jason

/Jarkko
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