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Fri, 4 Mar 2022 18:34:06 +0000 (GMT) Message-ID: <8b594101-f676-ca9d-ebe5-337470a3de80@linux.ibm.com> Date: Fri, 4 Mar 2022 13:34:06 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [PATCH v9 1/1] tpm: fix reference counting for struct tpm_chip Content-Language: en-US To: Jarkko Sakkinen , Lino Sanfilippo Cc: peterhuewe@gmx.de, jgg@ziepe.ca, stefanb@linux.vnet.ibm.com, James.Bottomley@hansenpartnership.com, David.Laight@aculab.com, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, p.rosenberger@kunbus.com, Lino Sanfilippo , stable@vger.kernel.org References: <20220302094353.3465-1-LinoSanfilippo@gmx.de> <20220302094353.3465-2-LinoSanfilippo@gmx.de> From: Stefan Berger In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: h9i3nsrFsvdPNGloOfsLgWKeC3o-gTFH X-Proofpoint-ORIG-GUID: zXGS_d4Df-eO0cVUWYOjwRqRTi2R26y6 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.64.514 definitions=2022-03-04_08,2022-03-04_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 impostorscore=0 phishscore=0 priorityscore=1501 spamscore=0 clxscore=1015 suspectscore=0 lowpriorityscore=0 adultscore=0 malwarescore=0 mlxscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2203040093 Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org On 3/3/22 17:45, Jarkko Sakkinen wrote: > On Wed, Mar 02, 2022 at 10:43:53AM +0100, Lino Sanfilippo wrote: >> From: Lino Sanfilippo >> >> 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 >> [] (unwind_backtrace) from [] (show_stack+0x10/0x14) >> [] (show_stack) from [] (dump_stack+0xc4/0xd8) >> [] (dump_stack) from [] (__warn+0x104/0x108) >> [] (__warn) from [] (warn_slowpath_fmt+0x74/0xb8) >> [] (warn_slowpath_fmt) from [] (kobject_get+0xa0/0xa4) >> [] (kobject_get) from [] (tpm_try_get_ops+0x14/0x54 [tpm]) >> [] (tpm_try_get_ops [tpm]) from [] (tpm_common_write+0x38/0x60 [tpm]) >> [] (tpm_common_write [tpm]) from [] (vfs_write+0xc4/0x3c0) >> [] (vfs_write) from [] (ksys_write+0x58/0xcc) >> [] (ksys_write) from [] (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") >> 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") >> Fixes: 8979b02aaf1d ("tpm: Fix reference count to main device") >> Co-developed-by: Jason Gunthorpe >> Tested-by: Stefan Berger >> Signed-off-by: Jason Gunthorpe >> Signed-off-by: Lino Sanfilippo >> --- >> 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(-) >> >> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c >> index b009e7479b70..783d65fc71f0 100644 >> --- a/drivers/char/tpm/tpm-chip.c >> +++ b/drivers/char/tpm/tpm-chip.c >> @@ -274,14 +274,6 @@ static void tpm_dev_release(struct device *dev) >> 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 device *pdev, >> 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; >> @@ -352,29 +343,12 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev, >> 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; >> >> @@ -382,9 +356,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *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 device *pdev, >> 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 tpm_chip *chip) >> } >> >> if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) { >> - 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 tpm_chip *chip) >> 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; >> } >> >> @@ -654,7 +624,7 @@ void tpm_chip_unregister(struct tpm_chip *chip) >> hwrng_unregister(&chip->hwrng); >> tpm_bios_log_teardown(chip); >> if (chip->flags & TPM_CHIP_FLAG_TPM2 && !tpm_is_firmware_upgrade(chip)) >> - cdev_device_del(&chip->cdevs, &chip->devs); >> + tpm_devs_remove(chip); >> tpm_del_char_device(chip); >> } >> EXPORT_SYMBOL_GPL(tpm_chip_unregister); >> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h >> index 283f78211c3a..2163c6ee0d36 100644 >> --- a/drivers/char/tpm/tpm.h >> +++ b/drivers/char/tpm/tpm.h >> @@ -234,6 +234,8 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u8 *cmd, >> 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); >> diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c >> index 97e916856cf3..265ec72b1d81 100644 >> --- a/drivers/char/tpm/tpm2-space.c >> +++ b/drivers/char/tpm/tpm2-space.c >> @@ -574,3 +574,68 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space, >> 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; >> +} >> -- >> 2.35.1 >> > LGTM, thank you. > > Reviewed-by: Jarkko Sakkinen > > Stefan, if possible, for sanity check, redo test with v9. We need that other patch as well! Tested-by: Stefan Berger    Stefan > > BR, Jarkko