From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Tadeusz Struk <tadeusz.struk@intel.com>
Cc: "James Bottomley" <James.Bottomley@HansenPartnership.com>,
"Mantas Mikulėnas" <grawity@gmail.com>,
linux-integrity@vger.kernel.org
Subject: Re: Kernel 5.0 regression in /dev/tpm0 access
Date: Wed, 13 Mar 2019 15:59:26 +0200 [thread overview]
Message-ID: <20190313135926.GA6862@linux.intel.com> (raw)
In-Reply-To: <14297706-74ef-f178-3b65-e63289919117@intel.com>
On Tue, Mar 12, 2019 at 03:42:00PM -0700, Tadeusz Struk wrote:
> Hi Jarkko,
> On 3/11/19 6:09 AM, Jarkko Sakkinen wrote:
> > Tadeusz, why on earth the code does not lock buffer_mutex?? Just noticed
> > when I checked the function in question. It is an awful bug alone.
>
> Because the tpm_common_poll() just reads the flags and doesn't modify
> them, so the logic was that if the response_length is not 0 or
> response_read is flase then the first poll should return EPOLLIN
> and if not, the application should call the poll again and only call read
> if the EPOLLIN is set in the mask. It looks like the tpm_timeout_work()
> kicks in and messes things out.
1. You have *two* variables that you read, which can lead up reading
a partial state.
2. You are not using atomic_t even if there was one variable.
> Looking at it again I think the response_read flag is redundant
> and only the response_length should be used.
Please provide a minimal fix to the issue. Only the fix for lock is
needed and send a proper patch (did not read the code below).
/Jarkko
next prev parent reply other threads:[~2019-03-13 13:59 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-09 20:48 Kernel 5.0 regression in /dev/tpm0 access Mantas Mikulėnas
2019-03-09 22:01 ` James Bottomley
2019-03-09 22:44 ` James Bottomley
2019-03-11 13:09 ` Jarkko Sakkinen
2019-03-12 22:42 ` Tadeusz Struk
2019-03-12 22:50 ` James Bottomley
2019-03-13 14:00 ` Jarkko Sakkinen
2019-03-13 13:59 ` Jarkko Sakkinen [this message]
2019-03-17 13:22 ` Jarkko Sakkinen
2019-03-18 15:50 ` Tadeusz Struk
2019-03-20 9:58 ` Jarkko Sakkinen
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