lkml.org 
[lkml]   [2022]   [Apr]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.16 0029/1017] tpm: fix reference counting for struct tpm_chip
    Date
    From: Lino Sanfilippo <LinoSanfilippo@gmx.de>

    commit 7e0438f83dc769465ee663bb5dcf8cc154940712 upstream.

    The following sequence of operations results in a refcount warning:

    1. Open device /dev/tpmrm.
    2. Remove module tpm_tis_spi.
    3. Write a TPM command to the file descriptor opened at step 1.

    ------------[ cut here ]------------
    WARNING: CPU: 3 PID: 1161 at lib/refcount.c:25 kobject_get+0xa0/0xa4
    refcount_t: addition on 0; use-after-free.
    Modules linked in: tpm_tis_spi tpm_tis_core tpm mdio_bcm_unimac brcmfmac
    sha256_generic libsha256 sha256_arm hci_uart btbcm bluetooth cfg80211 vc4
    brcmutil ecdh_generic ecc snd_soc_core crc32_arm_ce libaes
    raspberrypi_hwmon ac97_bus snd_pcm_dmaengine bcm2711_thermal snd_pcm
    snd_timer genet snd phy_generic soundcore [last unloaded: spi_bcm2835]
    CPU: 3 PID: 1161 Comm: hold_open Not tainted 5.10.0ls-main-dirty #2
    Hardware name: BCM2711
    [<c0410c3c>] (unwind_backtrace) from [<c040b580>] (show_stack+0x10/0x14)
    [<c040b580>] (show_stack) from [<c1092174>] (dump_stack+0xc4/0xd8)
    [<c1092174>] (dump_stack) from [<c0445a30>] (__warn+0x104/0x108)
    [<c0445a30>] (__warn) from [<c0445aa8>] (warn_slowpath_fmt+0x74/0xb8)
    [<c0445aa8>] (warn_slowpath_fmt) from [<c08435d0>] (kobject_get+0xa0/0xa4)
    [<c08435d0>] (kobject_get) from [<bf0a715c>] (tpm_try_get_ops+0x14/0x54 [tpm])
    [<bf0a715c>] (tpm_try_get_ops [tpm]) from [<bf0a7d6c>] (tpm_common_write+0x38/0x60 [tpm])
    [<bf0a7d6c>] (tpm_common_write [tpm]) from [<c05a7ac0>] (vfs_write+0xc4/0x3c0)
    [<c05a7ac0>] (vfs_write) from [<c05a7ee4>] (ksys_write+0x58/0xcc)
    [<c05a7ee4>] (ksys_write) from [<c04001a0>] (ret_fast_syscall+0x0/0x4c)
    Exception stack(0xc226bfa8 to 0xc226bff0)
    bfa0: 00000000 000105b4 00000003 beafe664 00000014 00000000
    bfc0: 00000000 000105b4 000103f8 00000004 00000000 00000000 b6f9c000 beafe684
    bfe0: 0000006c beafe648 0001056c b6eb6944
    ---[ end trace d4b8409def9b8b1f ]---

    The reason for this warning is the attempt to get the chip->dev reference
    in tpm_common_write() although the reference counter is already zero.

    Since commit 8979b02aaf1d ("tpm: Fix reference count to main device") the
    extra reference used to prevent a premature zero counter is never taken,
    because the required TPM_CHIP_FLAG_TPM2 flag is never set.

    Fix this by moving the TPM 2 character device handling from
    tpm_chip_alloc() to tpm_add_char_device() which is called at a later point
    in time when the flag has been set in case of TPM2.

    Commit fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
    already introduced function tpm_devs_release() to release the extra
    reference but did not implement the required put on chip->devs that results
    in the call of this function.

    Fix this by putting chip->devs in tpm_chip_unregister().

    Finally move the new implementation for the TPM 2 handling into a new
    function to avoid multiple checks for the TPM_CHIP_FLAG_TPM2 flag in the
    good case and error cases.

    Cc: stable@vger.kernel.org
    Fixes: fdc915f7f719 ("tpm: expose spaces via a device link /dev/tpmrm<n>")
    Fixes: 8979b02aaf1d ("tpm: Fix reference count to main device")
    Co-developed-by: Jason Gunthorpe <jgg@ziepe.ca>
    Signed-off-by: Jason Gunthorpe <jgg@ziepe.ca>
    Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
    Tested-by: Stefan Berger <stefanb@linux.ibm.com>
    Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
    Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
    Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/char/tpm/tpm-chip.c | 46 +++++------------------------
    drivers/char/tpm/tpm.h | 2 +
    drivers/char/tpm/tpm2-space.c | 65 ++++++++++++++++++++++++++++++++++++++++++
    3 files changed, 75 insertions(+), 38 deletions(-)

    --- a/drivers/char/tpm/tpm-chip.c
    +++ b/drivers/char/tpm/tpm-chip.c
    @@ -274,14 +274,6 @@ static void tpm_dev_release(struct devic
    kfree(chip);
    }

    -static void tpm_devs_release(struct device *dev)
    -{
    - struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
    -
    - /* release the master device reference */
    - put_device(&chip->dev);
    -}
    -
    /**
    * tpm_class_shutdown() - prepare the TPM device for loss of power.
    * @dev: device to which the chip is associated.
    @@ -344,7 +336,6 @@ struct tpm_chip *tpm_chip_alloc(struct d
    chip->dev_num = rc;

    device_initialize(&chip->dev);
    - device_initialize(&chip->devs);

    chip->dev.class = tpm_class;
    chip->dev.class->shutdown_pre = tpm_class_shutdown;
    @@ -352,39 +343,20 @@ struct tpm_chip *tpm_chip_alloc(struct d
    chip->dev.parent = pdev;
    chip->dev.groups = chip->groups;

    - chip->devs.parent = pdev;
    - chip->devs.class = tpmrm_class;
    - chip->devs.release = tpm_devs_release;
    - /* get extra reference on main device to hold on
    - * behalf of devs. This holds the chip structure
    - * while cdevs is in use. The corresponding put
    - * is in the tpm_devs_release (TPM2 only)
    - */
    - if (chip->flags & TPM_CHIP_FLAG_TPM2)
    - get_device(&chip->dev);
    -
    if (chip->dev_num == 0)
    chip->dev.devt = MKDEV(MISC_MAJOR, TPM_MINOR);
    else
    chip->dev.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num);

    - chip->devs.devt =
    - MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
    -
    rc = dev_set_name(&chip->dev, "tpm%d", chip->dev_num);
    if (rc)
    goto out;
    - rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
    - if (rc)
    - goto out;

    if (!pdev)
    chip->flags |= TPM_CHIP_FLAG_VIRTUAL;

    cdev_init(&chip->cdev, &tpm_fops);
    - cdev_init(&chip->cdevs, &tpmrm_fops);
    chip->cdev.owner = THIS_MODULE;
    - chip->cdevs.owner = THIS_MODULE;

    rc = tpm2_init_space(&chip->work_space, TPM2_SPACE_BUFFER_SIZE);
    if (rc) {
    @@ -396,7 +368,6 @@ struct tpm_chip *tpm_chip_alloc(struct d
    return chip;

    out:
    - put_device(&chip->devs);
    put_device(&chip->dev);
    return ERR_PTR(rc);
    }
    @@ -445,14 +416,9 @@ static int tpm_add_char_device(struct tp
    }

    if (chip->flags & TPM_CHIP_FLAG_TPM2) {
    - rc = cdev_device_add(&chip->cdevs, &chip->devs);
    - if (rc) {
    - dev_err(&chip->devs,
    - "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
    - dev_name(&chip->devs), MAJOR(chip->devs.devt),
    - MINOR(chip->devs.devt), rc);
    - return rc;
    - }
    + rc = tpm_devs_add(chip);
    + if (rc)
    + goto err_del_cdev;
    }

    /* Make the chip available. */
    @@ -460,6 +426,10 @@ static int tpm_add_char_device(struct tp
    idr_replace(&dev_nums_idr, chip, chip->dev_num);
    mutex_unlock(&idr_lock);

    + return 0;
    +
    +err_del_cdev:
    + cdev_device_del(&chip->cdev, &chip->dev);
    return rc;
    }

    @@ -649,7 +619,7 @@ void tpm_chip_unregister(struct tpm_chip
    hwrng_unregister(&chip->hwrng);
    tpm_bios_log_teardown(chip);
    if (chip->flags & TPM_CHIP_FLAG_TPM2)
    - cdev_device_del(&chip->cdevs, &chip->devs);
    + tpm_devs_remove(chip);
    tpm_del_char_device(chip);
    }
    EXPORT_SYMBOL_GPL(tpm_chip_unregister);
    --- a/drivers/char/tpm/tpm.h
    +++ b/drivers/char/tpm/tpm.h
    @@ -234,6 +234,8 @@ int tpm2_prepare_space(struct tpm_chip *
    size_t cmdsiz);
    int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space, void *buf,
    size_t *bufsiz);
    +int tpm_devs_add(struct tpm_chip *chip);
    +void tpm_devs_remove(struct tpm_chip *chip);

    void tpm_bios_log_setup(struct tpm_chip *chip);
    void tpm_bios_log_teardown(struct tpm_chip *chip);
    --- a/drivers/char/tpm/tpm2-space.c
    +++ b/drivers/char/tpm/tpm2-space.c
    @@ -574,3 +574,68 @@ out:
    dev_err(&chip->dev, "%s: error %d\n", __func__, rc);
    return rc;
    }
    +
    +/*
    + * Put the reference to the main device.
    + */
    +static void tpm_devs_release(struct device *dev)
    +{
    + struct tpm_chip *chip = container_of(dev, struct tpm_chip, devs);
    +
    + /* release the master device reference */
    + put_device(&chip->dev);
    +}
    +
    +/*
    + * Remove the device file for exposed TPM spaces and release the device
    + * reference. This may also release the reference to the master device.
    + */
    +void tpm_devs_remove(struct tpm_chip *chip)
    +{
    + cdev_device_del(&chip->cdevs, &chip->devs);
    + put_device(&chip->devs);
    +}
    +
    +/*
    + * Add a device file to expose TPM spaces. Also take a reference to the
    + * main device.
    + */
    +int tpm_devs_add(struct tpm_chip *chip)
    +{
    + int rc;
    +
    + device_initialize(&chip->devs);
    + chip->devs.parent = chip->dev.parent;
    + chip->devs.class = tpmrm_class;
    +
    + /*
    + * Get extra reference on main device to hold on behalf of devs.
    + * This holds the chip structure while cdevs is in use. The
    + * corresponding put is in the tpm_devs_release.
    + */
    + get_device(&chip->dev);
    + chip->devs.release = tpm_devs_release;
    + chip->devs.devt = MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
    + cdev_init(&chip->cdevs, &tpmrm_fops);
    + chip->cdevs.owner = THIS_MODULE;
    +
    + rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
    + if (rc)
    + goto err_put_devs;
    +
    + rc = cdev_device_add(&chip->cdevs, &chip->devs);
    + if (rc) {
    + dev_err(&chip->devs,
    + "unable to cdev_device_add() %s, major %d, minor %d, err=%d\n",
    + dev_name(&chip->devs), MAJOR(chip->devs.devt),
    + MINOR(chip->devs.devt), rc);
    + goto err_put_devs;
    + }
    +
    + return 0;
    +
    +err_put_devs:
    + put_device(&chip->devs);
    +
    + return rc;
    +}

    \
     
     \ /
      Last update: 2022-04-05 13:52    [W:4.029 / U:0.460 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site