On Thu, Feb 04, 2021 at 04:34:11PM -0800, James Bottomley wrote:
On Fri, 2021-02-05 at 00:50 +0100, Lino Sanfilippo wrote:
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);
}
Actually, this still isn't right. As I said to the last person who reported this, we should be doing a get/put on the ops, not rolling our own here:
https://lore.kernel.org/linux-integrity/e7566e1e48f5be9dca034b4bfb67683b5d3c...
The reporter went silent before we could get this tested, but could you try, please, because your patch is still hand rolling the ops get/put, just slightly better than it had been done previously.
James
Thanks for pointing this out. I'd strongly support Jason's proposal:
https://lore.kernel.org/linux-integrity/20201215175624.GG5487@ziepe.ca/
It's the best long-term way to fix this.
Honestly, I have to admit that this thread leaked from me. It happened exactly at the time when I was on vacation. Something must have gone wrong when I pulled emails after that.
/Jarkko