linux-kernel - [PATCH AUTOSEL 5.4 9/9] tpm: End any active auth session before shutdown

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Message-Id: <20250403192050.2682427-9-sashal@kernel.org>
Date: Thu,  3 Apr 2025 15:20:50 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Jonathan McDowell <noodles@...a.com>,
	Jarkko Sakkinen <jarkko@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	peterhuewe@....de,
	linux-integrity@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 9/9] tpm: End any active auth session before shutdown

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

[ Upstream commit 1dbf74e00a5f882b04b398399b6def65cd51ef21 ]

Lazy flushing of TPM auth sessions can interact badly with IMA + kexec,
resulting in loaded session handles being leaked across the kexec and
not cleaned up. Fix by ensuring any active auth session is ended before
the TPM is told about the shutdown, matching what is done when
suspending.

Before:

root@...ian-qemu-efi:~# tpm2_getcap handles-loaded-session
root@...ian-qemu-efi:~# tpm2_getcap handles-saved-session
root@...ian-qemu-efi:~# kexec --load --kexec-file-syscall …
root@...ian-qemu-efi:~# systemctl kexec
…
root@...ian-qemu-efi:~# tpm2_getcap handles-loaded-session
- 0x2000000
root@...ian-qemu-efi:~# tpm2_getcap handles-saved-session
root@...ian-qemu-efi:~#
(repeat kexec steps)
root@...ian-qemu-efi:~# tpm2_getcap handles-loaded-session
- 0x2000000
- 0x2000001
root@...ian-qemu-efi:~# tpm2_getcap handles-saved-session
root@...ian-qemu-efi:~#

After:

root@...ian-qemu-efi:~# tpm2_getcap handles-loaded-session
root@...ian-qemu-efi:~# tpm2_getcap handles-saved-session
root@...ian-qemu-efi:~# kexec --load --kexec-file-syscall …
root@...ian-qemu-efi:~# systemctl kexec
…
root@...ian-qemu-efi:~# tpm2_getcap handles-loaded-session
root@...ian-qemu-efi:~# tpm2_getcap handles-saved-session
root@...ian-qemu-efi:~#

Signed-off-by: Jonathan McDowell <noodles@...a.com>
Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/char/tpm/tpm-chip.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 17fbd7f7a2954..b33e938d80e8a 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -290,6 +290,7 @@ static int tpm_class_shutdown(struct device *dev)
 	down_write(&chip->ops_sem);
 	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
 		if (!tpm_chip_start(chip)) {
+			tpm2_end_auth_session(chip);
 			tpm2_shutdown(chip, TPM2_SU_CLEAR);
 			tpm_chip_stop(chip);
 		}
-- 
2.39.5