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From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Sergey Temerkhanov <s.temerkhanov@gmail.com>,
	Peter Huewe <peterhuewe@gmx.de>,
	Jarkko Sakkinen <jarkko@kernel.org>,
	Jason Gunthorpe <jgg@ziepe.ca>,
	Jerry Snitselaar <jsnitsel@redhat.com>,
	linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] tpm: Rework open/close/shutdown to avoid races
Date: Tue, 15 Dec 2020 10:51:43 -0800	[thread overview]
Message-ID: <e7566e1e48f5be9dca034b4bfb67683b5d3cb88f.camel@HansenPartnership.com> (raw)
In-Reply-To: <20201215133801.546207-1-s.temerkhanov@gmail.com>

On Tue, 2020-12-15 at 16:38 +0300, Sergey Temerkhanov wrote:
> Avoid race condition at shutdown by shutting downn the TPM 2.0
> devices synchronously. This eliminates the condition when the
> shutdown sequence sets chip->ops to NULL leading to the following:
> 
> [ 1586.593561][ T8669] tpm2_del_space+0x28/0x73
> [ 1586.598718][ T8669] tpmrm_release+0x27/0x33wq
> [ 1586.603774][ T8669] __fput+0x109/0x1d
> [ 1586.608380][ T8669] task_work_run+0x7c/0x90
> [ 1586.613414][ T8669] prepare_exit_to_usermode+0xb8/0x128
> [ 1586.619522][ T8669] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 1586.626068][ T8669] RIP: 0033:0x4cb4bb

An actual bug report would have been helpful.  However, from this trace
it's easy to deduce that tpm2_del_space() didn't get converted to the
get/put of the chip ops ... it's still trying to do its own half arsed
thing with tpm_chip_start() and the mutex.  So isn't a much simpler fix
simply to convert it as below?  compile tested only, but if you can
test it out I'll send a proper patch.

James

---

diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 784b8b3cb903..0c0cd225046f 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -58,12 +58,12 @@ int tpm2_init_space(struct tpm_space *space, unsigned int buf_size)
 
 void tpm2_del_space(struct tpm_chip *chip, struct tpm_space *space)
 {
-	mutex_lock(&chip->tpm_mutex);
-	if (!tpm_chip_start(chip)) {
+
+	if (tpm_try_get_ops(chip) == 0) {
 		tpm2_flush_sessions(chip, space);
-		tpm_chip_stop(chip);
+		tpm_put_ops(chip);
 	}
-	mutex_unlock(&chip->tpm_mutex);
+
 	kfree(space->context_buf);
 	kfree(space->session_buf);
 }


  parent reply	other threads:[~2020-12-15 18:54 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-15 13:38 Sergey Temerkhanov
2020-12-15 17:08 ` kernel test robot
2020-12-15 17:56 ` Jason Gunthorpe
2020-12-15 18:51 ` James Bottomley [this message]
2020-12-17 21:05   ` James Bottomley
2022-03-07 15:41   ` Jarkko Sakkinen
2022-03-07 16:22     ` James Bottomley
2022-03-07 16:44       ` Jarkko Sakkinen
2022-03-07 16:45         ` Jarkko Sakkinen

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