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Subject[PATCH v3 2/2] tpm: in tpm2_del_space check if ops pointer is still valid
Date
From: Lino Sanfilippo <l.sanfilippo@kunbus.com>

In tpm2_del_space() chip->ops is used for flushing the sessions. However
this function may be called after tpm_chip_unregister() which sets
the chip->ops pointer to NULL.
Avoid a possible NULL pointer dereference by checking if chip->ops is still
valid before accessing it.

Fixes: a3fbfae82b4c ("tpm: take TPM chip power gating out of tpm_transmit()")
Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
drivers/char/tpm/tpm2-space.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
index 784b8b3..9a29a40 100644
--- a/drivers/char/tpm/tpm2-space.c
+++ b/drivers/char/tpm/tpm2-space.c
@@ -58,12 +58,17 @@ 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)) {
- tpm2_flush_sessions(chip, space);
- tpm_chip_stop(chip);
+ down_read(&chip->ops_sem);
+ if (chip->ops) {
+ mutex_lock(&chip->tpm_mutex);
+ if (!tpm_chip_start(chip)) {
+ tpm2_flush_sessions(chip, space);
+ tpm_chip_stop(chip);
+ }
+ mutex_unlock(&chip->tpm_mutex);
}
- mutex_unlock(&chip->tpm_mutex);
+ up_read(&chip->ops_sem);
+
kfree(space->context_buf);
kfree(space->session_buf);
}
--
2.7.4
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