tpm: fix reference counting for struct tpm_chip

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>

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index b009e7479b702f861997beed160b33be5a97d479..783d65fc71f07da60dc777a0a3cd4b76f3ad2366 100644 (file)
--- 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 283f78211c3a7bc09092085d12834c48571f93f3..2163c6ee0d364f3f8ee935e5abae8f547b4a886f 100644 (file)
--- 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 97e916856cf3e25445c94256dbe94569f5e84524..265ec72b1d81614620ff9cf9f4636d1ba11e803e 100644 (file)
--- 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;
+}