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From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Kai-Heng Feng <kai.heng.feng@canonical.com>,
	"Kenneth R. Crudup" <kenny@panix.com>,
	Tyler Hicks <tyhicks@linux.microsoft.com>,
	linux-integrity <linux-integrity@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	Matthew Garrett <mjg59@google.com>,
	tweek@google.com
Subject: Re: [Regression] "tpm: Require that all digests are present in TCG_PCR_EVENT2 structures" causes null pointer dereference
Date: Mon, 28 Sep 2020 20:12:39 +0300	[thread overview]
Message-ID: <20200928171238.GB119268@linux.intel.com> (raw)
In-Reply-To: <CAMj1kXF-hOTZ62_Tf_GAN9_w7ztngdVp_atNrowH5Y0SwSjCAw@mail.gmail.com>

On Mon, Sep 28, 2020 at 06:15:00PM +0200, Ard Biesheuvel wrote:
> > > > It is possible but initially feels a bit weird:
> > > >
> > > > -                  sizeof(TCG_SPECID_SIG)) || count > efispecid->num_algs) {
> > > > +                  sizeof(TCG_SPECID_SIG)) ||
> > > > +           !efispecid->num_algs || count != efispecid->num_algs) {

^^^

> In tpm2_bios_measurements_start(), we dereference tpm_bios_log to
> access bios_event_log and bios_event_log_end without checking tpm_bios
> for NULL. This is where the crash seems to occur.

That's a good guess. Just a bit confused how that particular patch can
have the effect: it has two deferences to efispecid instead of one in
the same statement. Would be interesting to hear if the bug is triggered
in Kenneth's environment by the exact same commit.

/Jarkko

  parent reply	other threads:[~2020-09-28 17:12 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-28 12:31 Kai-Heng Feng
2020-09-28 14:06 ` Jarkko Sakkinen
2020-09-28 14:16   ` Kai-Heng Feng
     [not found]     ` <20200928155215.GA92669@linux.intel.com>
2020-09-28 16:15       ` Ard Biesheuvel
2020-09-28 16:26         ` Ard Biesheuvel
2020-09-28 17:12         ` Jarkko Sakkinen [this message]
2020-09-28 18:05           ` Kenneth R. Crudup
2020-09-29 17:52     ` Mimi Zohar
2020-09-30  2:20       ` Jarkko Sakkinen
2020-10-08  9:09         ` Kai-Heng Feng
2020-10-09 16:06           ` Jarkko Sakkinen
2020-10-13 14:31             ` Tyler Hicks
2020-10-13 14:33               ` Jarkko Sakkinen
2020-10-20 21:07       ` Mimi Zohar
2020-10-21  5:48         ` Tyler Hicks
2020-10-26  5:49           ` Kai-Heng Feng
2020-10-27  5:08             ` Tyler Hicks
2020-10-28 15:41 ` [PATCH] tpm: efi: Don't create binary_bios_measurements file for an empty log Tyler Hicks
2020-10-28 16:30   ` Tyler Hicks
2020-10-28 17:39     ` Tyler Hicks
2020-10-30  6:41       ` Kai-Heng Feng
2020-11-04  2:12       ` Kenneth R. Crudup
2020-10-30  4:46   ` Jarkko Sakkinen

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