On 6/15/21 05:14, Vincent Whitchurch wrote:
If the tpm_tis module is removed (or a system shutdown is triggered)
while the tpmrm device is use, the kernel crashes due to chip->ops being
NULL:
# exec 3<>/dev/tpmrm0
# rmmod tpm_tis
# exit
==================================================================
BUG: KASAN: null-ptr-deref in tpm_chip_start+0x2d/0x120 [tpm]
Read of size 8 at addr 0000000000000060 by task sh/994
Call Trace:
kasan_report.cold.13+0x10f/0x111
tpm_chip_start+0x2d/0x120 [tpm]
tpm2_del_space+0x2c/0xa0 [tpm]
tpmrm_release+0x3f/0x50 [tpm]
__fput+0x110/0x3c0
task_work_run+0x94/0xd0
do_exit+0x683/0x13e0
do_group_exit+0x8b/0x140
do_syscall_64+0x3c/0x80
==================================================================
Fix this by making tpm2_del_space() use tpm_try_get_ops(). The latter
already includes the calls to tpm_chip_start() and tpm_chip_stop().
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
As a follow-up to this message here: https://lkml.org/lkml/2022/3/1/552
Tested-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
---
drivers/char/tpm/tpm2-space.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 784b8b3cb903..e1111261021f 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -58,12 +58,10 @@ 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)) {
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);
}
