From: Tadeusz Struk <tadeusz.struk@intel.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>,
jarkko.sakkinen@linux.intel.com
Cc: jgg@ziepe.ca, linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] tpm: add support for partial reads
Date: Thu, 19 Jul 2018 14:01:16 -0700 [thread overview]
Message-ID: <0e9d3267-b9f4-2f56-9470-36931ae8f685@intel.com> (raw)
In-Reply-To: <1532032049.3061.1.camel@HansenPartnership.com>
On 07/19/2018 01:27 PM, James Bottomley wrote:
> On Thu, 2018-07-19 at 13:12 -0700, Tadeusz Struk wrote:
>> On 07/19/2018 12:52 PM, James Bottomley wrote:
>>> The ABI break is the error case as I outlined above. We can't
>>> assume everyone uses the current interface without getting an error
>>> and one error and your hosed is a nasty failure case to change the
>>> interface to.
>>
>> Well, if there is a broken application out there that doesn't work
>> today it will not work after this change neither.
>
> It doesn't have to be broken ... it could be using EFAULT to probe the
> buffer size for instance. That's the point of not breaking the ABI:
> you don't second guess what applications are doing.
>
Looking at the existing implementation again:
https://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security.git/tree/drivers/char/tpm/tpm-dev-common.c?h=next-tpm#n56
EFAULT is returned only if the copy_to_user() fails.
So today, if an application wants read 1 byte of a response, and provides
1 byte buffer for it, then only 1 byte of the response will be copied,
no error code will be returned, and the rest of the response will be gone.
I don't really see how and why would anyone use EFAULT err to probe for
the buffer size. That would really be a broken application.
Thanks,
--
Tadeusz
next prev parent reply other threads:[~2018-07-19 21:01 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-19 15:52 [PATCH] tpm: add support for partial reads Tadeusz Struk
2018-07-19 15:55 ` Tadeusz Struk
2018-07-19 17:19 ` James Bottomley
2018-07-19 17:54 ` Tadeusz Struk
2018-07-19 18:47 ` James Bottomley
2018-07-19 19:05 ` Tadeusz Struk
2018-07-19 19:52 ` James Bottomley
2018-07-19 20:12 ` Tadeusz Struk
2018-07-19 20:27 ` James Bottomley
2018-07-19 21:01 ` Tadeusz Struk [this message]
2018-07-23 20:19 ` Jarkko Sakkinen
2018-07-23 20:53 ` Tadeusz Struk
2018-07-23 21:13 ` James Bottomley
2018-07-23 21:38 ` Tadeusz Struk
2018-07-23 21:56 ` Jason Gunthorpe
2018-07-23 22:00 ` Tadeusz Struk
2018-07-23 22:08 ` Jason Gunthorpe
2018-07-23 23:42 ` Tadeusz Struk
2018-07-24 2:05 ` Jason Gunthorpe
2018-07-23 21:48 ` Jason Gunthorpe
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