[PATCH v4] tpm: fix reference counting for struct tpm_chip

[PATCH v4] tpm: fix reference counting for struct tpm_chip

[Lino Sanfilippo]

From: Lino Sanfilippo <l.sanfilippo@kunbus.com>

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 implemenation 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.

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 <l.sanfilippo@kunbus.com>
Cc: stable@vger.kernel.org
---
 drivers/char/tpm/tpm-chip.c | 80 ++++++++++++++++++++++++++++-----------------
 1 file changed, 50 insertions(+), 30 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index ddaeceb..44cac3a 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -344,7 +344,6 @@ 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;
@@ -352,39 +351,20 @@ 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;
 
 	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 +376,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
 	return chip;
 
 out:
-	put_device(&chip->devs);
 	put_device(&chip->dev);
 	return ERR_PTR(rc);
 }
@@ -431,6 +410,46 @@ struct tpm_chip *tpmm_chip_alloc(struct device *pdev,
 }
 EXPORT_SYMBOL_GPL(tpmm_chip_alloc);
 
+static int tpm_add_tpm2_char_device(struct tpm_chip *chip)
+{
+	int rc;
+
+	device_initialize(&chip->devs);
+	chip->devs.parent = chip->dev.parent;
+	chip->devs.class = tpmrm_class;
+
+	rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
+	if (rc)
+		goto out_put_devs;
+	/*
+	 * 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 = 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 out_put_devs;
+	}
+
+	return 0;
+
+out_put_devs:
+	put_device(&chip->devs);
+
+	return rc;
+}
+
 static int tpm_add_char_device(struct tpm_chip *chip)
 {
 	int rc;
@@ -445,14 +464,9 @@ 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_add_tpm2_char_device(chip);
+		if (rc)
+			goto del_cdev;
 	}
 
 	/* Make the chip available. */
@@ -460,6 +474,10 @@ 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;
+
+del_cdev:
+	cdev_device_del(&chip->cdev, &chip->dev);
 	return rc;
 }
 
@@ -640,8 +658,10 @@ void tpm_chip_unregister(struct tpm_chip *chip)
 	if (IS_ENABLED(CONFIG_HW_RANDOM_TPM))
 		hwrng_unregister(&chip->hwrng);
 	tpm_bios_log_teardown(chip);
-	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
 		cdev_device_del(&chip->cdevs, &chip->devs);
+		put_device(&chip->devs);
+	}
 	tpm_del_char_device(chip);
 }
 EXPORT_SYMBOL_GPL(tpm_chip_unregister);
-- 
2.7.4

Re: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[Jarkko Sakkinen]

On Tue, Feb 16, 2021 at 01:31:00AM +0100, Lino Sanfilippo wrote:
> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> 
> The following sequence of operations results in a refcount warning:
> 
> 1. Open device /dev/tpmrm

Add '.' to end.

> 2. Remove module tpm_tis_spi

Add '.' to end.

> 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 implemenation 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.
> 
> 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 <l.sanfilippo@kunbus.com>
> Cc: stable@vger.kernel.org

Put Cc first.

> ---
>  drivers/char/tpm/tpm-chip.c | 80 ++++++++++++++++++++++++++++-----------------
>  1 file changed, 50 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index ddaeceb..44cac3a 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -344,7 +344,6 @@ 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;
> @@ -352,39 +351,20 @@ 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;
>  
>  	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 +376,6 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
>  	return chip;
>  
>  out:
> -	put_device(&chip->devs);
>  	put_device(&chip->dev);
>  	return ERR_PTR(rc);
>  }
> @@ -431,6 +410,46 @@ struct tpm_chip *tpmm_chip_alloc(struct device *pdev,
>  }
>  EXPORT_SYMBOL_GPL(tpmm_chip_alloc);
>  
> +static int tpm_add_tpm2_char_device(struct tpm_chip *chip)
> +{
> +	int rc;
> +
> +	device_initialize(&chip->devs);
> +	chip->devs.parent = chip->dev.parent;
> +	chip->devs.class = tpmrm_class;
> +
> +	rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
> +	if (rc)
> +		goto out_put_devs;
> +	/*
> +	 * 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 = 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 out_put_devs;
> +	}
> +
> +	return 0;
> +
> +out_put_devs:
> +	put_device(&chip->devs);
> +
> +	return rc;
> +}
> +
>  static int tpm_add_char_device(struct tpm_chip *chip)
>  {
>  	int rc;
> @@ -445,14 +464,9 @@ 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_add_tpm2_char_device(chip);
> +		if (rc)
> +			goto del_cdev;
>  	}
>  
>  	/* Make the chip available. */
> @@ -460,6 +474,10 @@ 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;
> +
> +del_cdev:
> +	cdev_device_del(&chip->cdev, &chip->dev);
>  	return rc;
>  }
>  
> @@ -640,8 +658,10 @@ void tpm_chip_unregister(struct tpm_chip *chip)
>  	if (IS_ENABLED(CONFIG_HW_RANDOM_TPM))
>  		hwrng_unregister(&chip->hwrng);
>  	tpm_bios_log_teardown(chip);
> -	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> +	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
>  		cdev_device_del(&chip->cdevs, &chip->devs);
> +		put_device(&chip->devs);
> +	}
>  	tpm_del_char_device(chip);
>  }
>  EXPORT_SYMBOL_GPL(tpm_chip_unregister);
> -- 
> 2.7.4
> 

Other than that, this looks good to me.

If this passes testing, I can fix those nit's.

I'll test this post 5.12 PR.

/Jarkko

Re: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[Jason Gunthorpe]

On Tue, Feb 16, 2021 at 01:31:00AM +0100, Lino Sanfilippo wrote:
>  
> +static int tpm_add_tpm2_char_device(struct tpm_chip *chip)
> +{
> +	int rc;
> +
> +	device_initialize(&chip->devs);
> +	chip->devs.parent = chip->dev.parent;
> +	chip->devs.class = tpmrm_class;
> +
> +	rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
> +	if (rc)
> +		goto out_put_devs;
> +	/*
> +	 * 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 = 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 out_put_devs;
> +	}
> +
> +	return 0;
> +
> +out_put_devs:
> +	put_device(&chip->devs);

I'd rather you organize this so chip->devs.release and the get_device
is always sent instead of having the possiblity for a put_device that
doesn't call release

Jason

Re: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[Jarkko Sakkinen]

On Tue, Feb 16, 2021 at 08:53:42AM -0400, Jason Gunthorpe wrote:
> On Tue, Feb 16, 2021 at 01:31:00AM +0100, Lino Sanfilippo wrote:
> >  
> > +static int tpm_add_tpm2_char_device(struct tpm_chip *chip)

BTW, this naming is crap.

- 2x tpm
- char is useless

-> tpm2_add_device


> > +{
> > +	int rc;
> > +
> > +	device_initialize(&chip->devs);
> > +	chip->devs.parent = chip->dev.parent;
> > +	chip->devs.class = tpmrm_class;
> > +
> > +	rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
> > +	if (rc)
> > +		goto out_put_devs;

Right, and empty line missing here.

> > +	/*
> > +	 * 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);

Isn't this less than 100 chars?

> > +	cdev_init(&chip->cdevs, &tpmrm_fops);
> > +	chip->cdevs.owner = THIS_MODULE;
> > +
> > +	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 out_put_devs;
> > +	}
> > +
> > +	return 0;
> > +
> > +out_put_devs:
> > +	put_device(&chip->devs);
> 
> I'd rather you organize this so chip->devs.release and the get_device
> is always sent instead of having the possiblity for a put_device that
> doesn't call release

/Jarkko

Re: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[Jarkko Sakkinen]

On Tue, Feb 16, 2021 at 06:04:42PM +0200, Jarkko Sakkinen wrote:
> On Tue, Feb 16, 2021 at 08:53:42AM -0400, Jason Gunthorpe wrote:
> > On Tue, Feb 16, 2021 at 01:31:00AM +0100, Lino Sanfilippo wrote:
> > >  
> > > +static int tpm_add_tpm2_char_device(struct tpm_chip *chip)
> 
> BTW, this naming is crap.
> 
> - 2x tpm
> - char is useless
> 
> -> tpm2_add_device

Actually, tpm2s_add_device() add put it to tpm2-space.c.

> > > +{
> > > +	int rc;
> > > +
> > > +	device_initialize(&chip->devs);
> > > +	chip->devs.parent = chip->dev.parent;
> > > +	chip->devs.class = tpmrm_class;
> > > +
> > > +	rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
> > > +	if (rc)
> > > +		goto out_put_devs;
> 
> Right, and empty line missing here.
> 
> > > +	/*
> > > +	 * 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);
> 
> Isn't this less than 100 chars?
> 
> > > +	cdev_init(&chip->cdevs, &tpmrm_fops);
> > > +	chip->cdevs.owner = THIS_MODULE;
> > > +
> > > +	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 out_put_devs;
> > > +	}
> > > +
> > > +	return 0;
> > > +
> > > +out_put_devs:
> > > +	put_device(&chip->devs);
> > 
> > I'd rather you organize this so chip->devs.release and the get_device
> > is always sent instead of having the possiblity for a put_device that
> > doesn't call release
> 
> /Jarkko

Re: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[Jarkko Sakkinen]

On Tue, Feb 16, 2021 at 06:09:50PM +0200, Jarkko Sakkinen wrote:
> On Tue, Feb 16, 2021 at 06:04:42PM +0200, Jarkko Sakkinen wrote:
> > On Tue, Feb 16, 2021 at 08:53:42AM -0400, Jason Gunthorpe wrote:
> > > On Tue, Feb 16, 2021 at 01:31:00AM +0100, Lino Sanfilippo wrote:
> > > >  
> > > > +static int tpm_add_tpm2_char_device(struct tpm_chip *chip)
> > 
> > BTW, this naming is crap.
> > 
> > - 2x tpm
> > - char is useless
> > 
> > -> tpm2_add_device
> 
> Actually, tpm2s_add_device() add put it to tpm2-space.c.

No, tpms_add_device() :-)

(sorry)

/Jarkko

> 
> > > > +{
> > > > +	int rc;
> > > > +
> > > > +	device_initialize(&chip->devs);
> > > > +	chip->devs.parent = chip->dev.parent;
> > > > +	chip->devs.class = tpmrm_class;
> > > > +
> > > > +	rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
> > > > +	if (rc)
> > > > +		goto out_put_devs;
> > 
> > Right, and empty line missing here.
> > 
> > > > +	/*
> > > > +	 * 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);
> > 
> > Isn't this less than 100 chars?
> > 
> > > > +	cdev_init(&chip->cdevs, &tpmrm_fops);
> > > > +	chip->cdevs.owner = THIS_MODULE;
> > > > +
> > > > +	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 out_put_devs;
> > > > +	}
> > > > +
> > > > +	return 0;
> > > > +
> > > > +out_put_devs:
> > > > +	put_device(&chip->devs);
> > > 
> > > I'd rather you organize this so chip->devs.release and the get_device
> > > is always sent instead of having the possiblity for a put_device that
> > > doesn't call release
> > 
> > /Jarkko

Re: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[Lino Sanfilippo]

Hi,

On 16.02.21 at 17:11, Jarkko Sakkinen wrote:
> On Tue, Feb 16, 2021 at 06:09:50PM +0200, Jarkko Sakkinen wrote:
>> On Tue, Feb 16, 2021 at 06:04:42PM +0200, Jarkko Sakkinen wrote:
>>> On Tue, Feb 16, 2021 at 08:53:42AM -0400, Jason Gunthorpe wrote:
>>>> On Tue, Feb 16, 2021 at 01:31:00AM +0100, Lino Sanfilippo wrote:
>>>>>
>>>>> +static int tpm_add_tpm2_char_device(struct tpm_chip *chip)
>>>
>>> BTW, this naming is crap.
>>>
>>> - 2x tpm
>>> - char is useless
>>>
>>> -> tpm2_add_device
>>
>> Actually, tpm2s_add_device() add put it to tpm2-space.c.
>
> No, tpms_add_device() :-)
>
> (sorry)
>
> /Jarkko
>

I strongly assume you mean tmp2_add_device() :) I will move and rename the function
accordingly.

Thanks,
Lino

RE: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[David Laight]

...
> > > +	get_device(&chip->dev);
> > > +	chip->devs.release = tpm_devs_release;
> > > +	chip->devs.devt =
> > > +		MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
> 
> Isn't this less than 100 chars?

Still best kept under 80 if 'reasonable'?

Really it is just split in the wrong place:
	chip->devs.devt = MKDEV(MAJOR(tpm_devt),
					chip->dev_num + TPM_NUM_DEVICES);

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[Jarkko Sakkinen]

On Tue, Feb 16, 2021 at 04:31:26PM +0000, David Laight wrote:
> ...
> > > > +	get_device(&chip->dev);
> > > > +	chip->devs.release = tpm_devs_release;
> > > > +	chip->devs.devt =
> > > > +		MKDEV(MAJOR(tpm_devt), chip->dev_num + TPM_NUM_DEVICES);
> > 
> > Isn't this less than 100 chars?
> 
> Still best kept under 80 if 'reasonable'?
> 
> Really it is just split in the wrong place:
> 	chip->devs.devt = MKDEV(MAJOR(tpm_devt),
> 					chip->dev_num + TPM_NUM_DEVICES);


Well it looks crap IMHO. Would be more reasonable to have it in a single 
like. And it is legit too, since it is accepted by checkpatch.

You might break the lines within 80 chars if it is somehow "logically"
consistent.

> 
> 	David
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
> 
> 

/Jarkko

Re: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[Lino Sanfilippo]

Hi

On 16.02.21 at 17:04, Jarkko Sakkinen wrote:

>>> +	/*
>>> +	 * 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);
>
> Isn't this less than 100 chars?
>

I just chose the same formatting that the original code used. Personally I prefer what
David suggested, so if there is no objection against it I will format it this way.

Regards,
Lino

Re: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[Lino Sanfilippo]

Hi,

On 16.02.21 at 13:53, Jason Gunthorpe wrote:
> On Tue, Feb 16, 2021 at 01:31:00AM +0100, Lino Sanfilippo wrote:
>>
>> +static int tpm_add_tpm2_char_device(struct tpm_chip *chip)
>> +{
>> +	int rc;
>> +
>> +	device_initialize(&chip->devs);
>> +	chip->devs.parent = chip->dev.parent;
>> +	chip->devs.class = tpmrm_class;
>> +
>> +	rc = dev_set_name(&chip->devs, "tpmrm%d", chip->dev_num);
>> +	if (rc)
>> +		goto out_put_devs;
>> +	/*
>> +	 * 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 = 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 out_put_devs;
>> +	}
>> +
>> +	return 0;
>> +
>> +out_put_devs:
>> +	put_device(&chip->devs);
>
> I'd rather you organize this so chip->devs.release and the get_device
> is always sent instead of having the possiblity for a put_device that
> doesn't call release
>

Agreed, I will change it. It should not make a difference in terms of correctness
but I see that it is less confusing if both error cases are handled similarly (plus its
only a minimal change).


Best regards,
Lino

Re: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[Stefan Berger]

On 2/15/21 7:31 PM, Lino Sanfilippo wrote:
> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>
> 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 implemenation 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.
>
> 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 <l.sanfilippo@kunbus.com>
> Cc: stable@vger.kernel.org


I know you'll post another version, but anyway:

Tested-by: Stefan Berger <stefanb@linux.ibm.com>

Re: [PATCH v4] tpm: fix reference counting for struct tpm_chip

[Lino Sanfilippo]

Hi Stefan,

On 16.02.21 at 17:52, Stefan Berger wrote:
> On 2/15/21 7:31 PM, Lino Sanfilippo wrote:
>> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>
>> 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 implemenation 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.
>>
>> 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 <l.sanfilippo@kunbus.com>
>> Cc: stable@vger.kernel.org
>
>
> I know you'll post another version, but anyway:
>
> Tested-by: Stefan Berger <stefanb@linux.ibm.com>

Thank you for testing this, I will send a v5 shortly.

Regards,
Lino