linux-kernel - [PATCH v2] tpm: Clean up TPM space after command failure

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Message-ID: <Zr8-QijwOpDLkol3@earth.li>
Date: Fri, 16 Aug 2024 12:55:46 +0100
From: Jonathan McDowell <noodles@...th.li>
To: Jarkko Sakkinen <jarkko@...nel.org>, Peter Huewe <peterhuewe@....de>,
	Jason Gunthorpe <jgg@...pe.ca>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] tpm: Clean up TPM space after command failure

From: Jonathan McDowell <noodles@...a.com>

tpm_dev_transmit prepares the TPM space before attempting command
transmission. However if the command fails no rollback of this
preparation is done. This can result in transient handles being leaked
if the device is subsequently closed with no further commands performed.

Fix this by flushing the space in the event of command transmission
failure.

Fixes: 745b361e989a ("tpm: infrastructure for TPM spaces")
Signed-off-by: Jonathan McDowell <noodles@...a.com>
---
v2:
 - Add 'Fixes:'
 - Cc James as one of the original authors
 - Add space sanity check in tpm2_flush_space

 drivers/char/tpm/tpm-dev-common.c | 2 ++
 drivers/char/tpm/tpm2-space.c     | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
index 30b4c288c1bb..c3fbbf4d3db7 100644
--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -47,6 +47,8 @@ static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
 
 	if (!ret)
 		ret = tpm2_commit_space(chip, space, buf, &len);
+	else
+		tpm2_flush_space(chip);
 
 out_rc:
 	return ret ? ret : len;
diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 4892d491da8d..25a66870c165 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -169,6 +169,9 @@ void tpm2_flush_space(struct tpm_chip *chip)
 	struct tpm_space *space = &chip->work_space;
 	int i;
 
+	if (!space)
+		return;
+
 	for (i = 0; i < ARRAY_SIZE(space->context_tbl); i++)
 		if (space->context_tbl[i] && ~space->context_tbl[i])
 			tpm2_flush_context(chip, space->context_tbl[i]);
-- 
2.46.0