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 --- 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 11ec5c2715a9..d91a795ad432 100644 --- a/drivers/char/tpm/tpm-chip.c +++ b/drivers/char/tpm/tpm-chip.c @@ -134,14 +134,6 @@ 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. @@ -205,7 +197,6 @@ 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; @@ -213,29 +204,12 @@ 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;

@@ -243,9 +217,7 @@ 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) { @@ -257,7 +229,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev, return chip;

out: - put_device(&chip->devs); put_device(&chip->dev); return ERR_PTR(rc); } @@ -306,14 +277,9 @@ static int tpm_add_char_device(struct tpm_chip *chip) }

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. */ @@ -321,6 +287,10 @@ 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; }

@@ -449,7 +419,7 @@ void tpm_chip_unregister(struct tpm_chip *chip) tpm_del_legacy_sysfs(chip); 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); diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h index 019fe80fedd8..7436da043040 100644 --- a/drivers/char/tpm/tpm.h +++ b/drivers/char/tpm/tpm.h @@ -593,4 +593,6 @@ int tpm2_prepare_space(struct tpm_chip *chip, struct tpm_space *space, u32 cc, u8 *cmd); int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space, u32 cc, u8 *buf, size_t *bufsiz); +int tpm_devs_add(struct tpm_chip *chip); +void tpm_devs_remove(struct tpm_chip *chip); #endif diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c index c7763a96cbaf..8e42bc096e83 100644 --- a/drivers/char/tpm/tpm2-space.c +++ b/drivers/char/tpm/tpm2-space.c @@ -540,3 +540,68 @@ int tpm2_commit_space(struct tpm_chip *chip, struct tpm_space *space,

return 0; } + +/* + * 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; +}