| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20201208110051.GA18099@linux.intel.com>
Date: Tue, 8 Dec 2020 13:00:51 +0200
From: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To: Sergey Temerkhanov <s.temerkhanov@...il.com>
Cc: Peter Huewe <peterhuewe@....de>, Jason Gunthorpe <jgg@...pe.ca>,
Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Jerry Snitselaar <jsnitsel@...hat.com>,
linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][RFC] tpm: Rework open/close/shutdown to avoid races
On Fri, Dec 04, 2020 at 01:18:05PM +0300, Sergey Temerkhanov wrote:
> Avoid race condition at shutdown by shutting downn the TPM 2.0
> devices synchronously. This eliminates the condition when the
> shutdown sequence sets chip->ops to NULL leading to the following:
>
> [ 1586.593561][ T8669] tpm2_del_space+0x28/0x73
> [ 1586.598718][ T8669] tpmrm_release+0x27/0x33wq
> [ 1586.603774][ T8669] __fput+0x109/0x1d
> [ 1586.608380][ T8669] task_work_run+0x7c/0x90
> [ 1586.613414][ T8669] prepare_exit_to_usermode+0xb8/0x128
> [ 1586.619522][ T8669] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [ 1586.626068][ T8669] RIP: 0033:0x4cb4bb
>
> Signed-off-by: Sergey Temerkhanov <s.temerkhanov@...il.com>
bitops is an atomic API. I don't understand why you want to convert
to "atomic_t". You are also removing tpm_class_shutdown() without
any explanation. Finally, there is no bug report.
/Jarkko
> ---
> drivers/char/tpm/tpm-chip.c | 27 ---------------------------
> drivers/char/tpm/tpm-dev.c | 11 ++++++-----
> drivers/char/tpm/tpmrm-dev.c | 7 +++++++
> include/linux/tpm.h | 2 +-
> 4 files changed, 14 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 1838039b0333..ede7f4790c5e 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -282,32 +282,6 @@ static void tpm_devs_release(struct device *dev)
> put_device(&chip->dev);
> }
>
> -/**
> - * tpm_class_shutdown() - prepare the TPM device for loss of power.
> - * @dev: device to which the chip is associated.
> - *
> - * Issues a TPM2_Shutdown command prior to loss of power, as required by the
> - * TPM 2.0 spec. Then, calls bus- and device- specific shutdown code.
> - *
> - * Return: always 0 (i.e. success)
> - */
> -static int tpm_class_shutdown(struct device *dev)
> -{
> - struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);
> -
> - down_write(&chip->ops_sem);
> - if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> - if (!tpm_chip_start(chip)) {
> - tpm2_shutdown(chip, TPM2_SU_CLEAR);
> - tpm_chip_stop(chip);
> - }
> - }
> - chip->ops = NULL;
> - up_write(&chip->ops_sem);
> -
> - return 0;
> -}
> -
> /**
> * tpm_chip_alloc() - allocate a new struct tpm_chip instance
> * @pdev: device to which the chip is associated
> @@ -347,7 +321,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> device_initialize(&chip->devs);
>
> chip->dev.class = tpm_class;
> - chip->dev.class->shutdown_pre = tpm_class_shutdown;
> chip->dev.release = tpm_dev_release;
> chip->dev.parent = pdev;
> chip->dev.groups = chip->groups;
> diff --git a/drivers/char/tpm/tpm-dev.c b/drivers/char/tpm/tpm-dev.c
> index e2c0baa69fef..e04f3d47c64e 100644
> --- a/drivers/char/tpm/tpm-dev.c
> +++ b/drivers/char/tpm/tpm-dev.c
> @@ -23,9 +23,9 @@ static int tpm_open(struct inode *inode, struct file *file)
> chip = container_of(inode->i_cdev, struct tpm_chip, cdev);
>
> /* It's assured that the chip will be opened just once,
> - * by the check of is_open variable, which is protected
> - * by driver_lock. */
> - if (test_and_set_bit(0, &chip->is_open)) {
> + * by the check of is_open variable
> + */
> + if (atomic_fetch_or(1, &chip->is_open)) {
> dev_dbg(&chip->dev, "Another process owns this TPM\n");
> return -EBUSY;
> }
> @@ -39,7 +39,7 @@ static int tpm_open(struct inode *inode, struct file *file)
> return 0;
>
> out:
> - clear_bit(0, &chip->is_open);
> + atomic_set(&chip->is_open, 0);
> return -ENOMEM;
> }
>
> @@ -49,9 +49,10 @@ static int tpm_open(struct inode *inode, struct file *file)
> static int tpm_release(struct inode *inode, struct file *file)
> {
> struct file_priv *priv = file->private_data;
> + struct tpm_chip *chip = priv->chip;
>
> tpm_common_release(file, priv);
> - clear_bit(0, &priv->chip->is_open);
> + atomic_set(&chip->is_open, 0);
> kfree(priv);
>
> return 0;
> diff --git a/drivers/char/tpm/tpmrm-dev.c b/drivers/char/tpm/tpmrm-dev.c
> index eef0fb06ea83..ec83ca8105b8 100644
> --- a/drivers/char/tpm/tpmrm-dev.c
> +++ b/drivers/char/tpm/tpmrm-dev.c
> @@ -27,6 +27,8 @@ static int tpmrm_open(struct inode *inode, struct file *file)
> return -ENOMEM;
> }
>
> + atomic_inc(&chip->is_open);
> +
> tpm_common_open(file, chip, &priv->priv, &priv->space);
>
> return 0;
> @@ -39,6 +41,11 @@ static int tpmrm_release(struct inode *inode, struct file *file)
>
> tpm_common_release(file, fpriv);
> tpm2_del_space(fpriv->chip, &priv->space);
> +
> + if (!atomic_dec_return(&fpriv->chip->is_open)) {
> + tpm2_shutdown(fpriv->chip, TPM2_SU_CLEAR);
> + tpm_chip_stop(fpriv->chip);
> + }
> kfree(priv);
>
> return 0;
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 77fdc988c610..26e070198a15 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -126,7 +126,7 @@ struct tpm_chip {
> unsigned int flags;
>
> int dev_num; /* /dev/tpm# */
> - unsigned long is_open; /* only one allowed */
> + atomic_t is_open; /* only one allowed */
>
> char hwrng_name[64];
> struct hwrng hwrng;
> --
> 2.25.1
>
/Jarkko
Powered by blists - more mailing lists