at24: fix memory corruption race condition

[PATCH v1] at24: fix memory corruption race condition

Posted by Daniel Okazaki 1 week, 6 days ago

If the eeprom is not accessible, an nvmem device will be registered, the
read will fail, and the device will be torn down. If another driver
accesses the nvmem device after the teardown, it will reference
invalid memory.

Move the failure point before registering the nvmem device.

Signed-off-by: Daniel Okazaki <dtokazaki@google.com>
---
 drivers/misc/eeprom/at24.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 572333ead5fb..4bd4f32bcdab 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -758,15 +758,6 @@ static int at24_probe(struct i2c_client *client)
 	}
 	pm_runtime_enable(dev);
 
-	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
-	if (IS_ERR(at24->nvmem)) {
-		pm_runtime_disable(dev);
-		if (!pm_runtime_status_suspended(dev))
-			regulator_disable(at24->vcc_reg);
-		return dev_err_probe(dev, PTR_ERR(at24->nvmem),
-				     "failed to register nvmem\n");
-	}
-
 	/*
 	 * Perform a one-byte test read to verify that the chip is functional,
 	 * unless powering on the device is to be avoided during probe (i.e.
@@ -782,6 +773,15 @@ static int at24_probe(struct i2c_client *client)
 		}
 	}
 
+	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
+	if (IS_ERR(at24->nvmem)) {
+		pm_runtime_disable(dev);
+		if (!pm_runtime_status_suspended(dev))
+			regulator_disable(at24->vcc_reg);
+		return dev_err_probe(dev, PTR_ERR(at24->nvmem),
+				     "failed to register nvmem\n");
+	}
+
 	/* If this a SPD EEPROM, probe for DDR3 thermal sensor */
 	if (cdata == &at24_data_spd)
 		at24_probe_temp_sensor(client);
-- 
2.44.0.683.g7961c838ac-goog

Re: [PATCH v1] at24: fix memory corruption race condition

Posted by Bartosz Golaszewski 1 week, 6 days ago

On Thu, Apr 18, 2024 at 1:07 AM Daniel Okazaki <dtokazaki@google.com> wrote:
>
> If the eeprom is not accessible, an nvmem device will be registered, the
> read will fail, and the device will be torn down. If another driver
> accesses the nvmem device after the teardown, it will reference
> invalid memory.
>
> Move the failure point before registering the nvmem device.
>
> Signed-off-by: Daniel Okazaki <dtokazaki@google.com>
> ---
>  drivers/misc/eeprom/at24.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 572333ead5fb..4bd4f32bcdab 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -758,15 +758,6 @@ static int at24_probe(struct i2c_client *client)
>         }
>         pm_runtime_enable(dev);
>
> -       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> -       if (IS_ERR(at24->nvmem)) {
> -               pm_runtime_disable(dev);
> -               if (!pm_runtime_status_suspended(dev))
> -                       regulator_disable(at24->vcc_reg);
> -               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> -                                    "failed to register nvmem\n");
> -       }
> -
>         /*
>          * Perform a one-byte test read to verify that the chip is functional,
>          * unless powering on the device is to be avoided during probe (i.e.
> @@ -782,6 +773,15 @@ static int at24_probe(struct i2c_client *client)
>                 }
>         }
>
> +       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> +       if (IS_ERR(at24->nvmem)) {
> +               pm_runtime_disable(dev);
> +               if (!pm_runtime_status_suspended(dev))
> +                       regulator_disable(at24->vcc_reg);
> +               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> +                                    "failed to register nvmem\n");
> +       }
> +
>         /* If this a SPD EEPROM, probe for DDR3 thermal sensor */
>         if (cdata == &at24_data_spd)
>                 at24_probe_temp_sensor(client);
> --
> 2.44.0.683.g7961c838ac-goog
>

Looks good, can you add a Fixes tag?

Thanks,
Bartosz

Re: [PATCH v1] at24: fix memory corruption race condition

Posted by Bartosz Golaszewski 1 week, 6 days ago

On Thu, Apr 18, 2024 at 1:59 AM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>
> On Thu, Apr 18, 2024 at 1:07 AM Daniel Okazaki <dtokazaki@google.com> wrote:
> >
> > If the eeprom is not accessible, an nvmem device will be registered, the
> > read will fail, and the device will be torn down. If another driver
> > accesses the nvmem device after the teardown, it will reference
> > invalid memory.
> >
> > Move the failure point before registering the nvmem device.
> >
> > Signed-off-by: Daniel Okazaki <dtokazaki@google.com>
> > ---
> >  drivers/misc/eeprom/at24.c | 18 +++++++++---------
> >  1 file changed, 9 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> > index 572333ead5fb..4bd4f32bcdab 100644
> > --- a/drivers/misc/eeprom/at24.c
> > +++ b/drivers/misc/eeprom/at24.c
> > @@ -758,15 +758,6 @@ static int at24_probe(struct i2c_client *client)
> >         }
> >         pm_runtime_enable(dev);
> >
> > -       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> > -       if (IS_ERR(at24->nvmem)) {
> > -               pm_runtime_disable(dev);
> > -               if (!pm_runtime_status_suspended(dev))
> > -                       regulator_disable(at24->vcc_reg);
> > -               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> > -                                    "failed to register nvmem\n");
> > -       }
> > -
> >         /*
> >          * Perform a one-byte test read to verify that the chip is functional,
> >          * unless powering on the device is to be avoided during probe (i.e.
> > @@ -782,6 +773,15 @@ static int at24_probe(struct i2c_client *client)
> >                 }
> >         }
> >
> > +       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> > +       if (IS_ERR(at24->nvmem)) {
> > +               pm_runtime_disable(dev);
> > +               if (!pm_runtime_status_suspended(dev))
> > +                       regulator_disable(at24->vcc_reg);
> > +               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> > +                                    "failed to register nvmem\n");
> > +       }
> > +
> >         /* If this a SPD EEPROM, probe for DDR3 thermal sensor */
> >         if (cdata == &at24_data_spd)
> >                 at24_probe_temp_sensor(client);
> > --
> > 2.44.0.683.g7961c838ac-goog
> >
>
> Looks good, can you add a Fixes tag?
>
> Thanks,
> Bartosz

Wait... While the patch is still correct - we shouldn't needlessly
create the nvmem device - why would anything crash? Looks like a
problem with nvmem then? How did you trigger this issue?

Bart

Re: [PATCH v1] at24: fix memory corruption race condition

Posted by Daniel Okazaki 1 week, 5 days ago

nvmem devices allow for linking by name in the DTS which doesn't
create a dependency in the probe order.

What happens is driver B probe starts shortly after the eeprom
probe and calls of_nvmem_device_get. Since a device is
registered it starts using it; however if the eeprom isn't there
then the read will fail and it will start tearing down the resources.
Driver B will now access invalid memory causing a kernel panic.

Daniel


On Wed, Apr 17, 2024 at 5:23 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>
> On Thu, Apr 18, 2024 at 1:59 AM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> >
> > On Thu, Apr 18, 2024 at 1:07 AM Daniel Okazaki <dtokazaki@google.com> wrote:
> > >
> > > If the eeprom is not accessible, an nvmem device will be registered, the
> > > read will fail, and the device will be torn down. If another driver
> > > accesses the nvmem device after the teardown, it will reference
> > > invalid memory.
> > >
> > > Move the failure point before registering the nvmem device.
> > >
> > > Signed-off-by: Daniel Okazaki <dtokazaki@google.com>
> > > ---
> > >  drivers/misc/eeprom/at24.c | 18 +++++++++---------
> > >  1 file changed, 9 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> > > index 572333ead5fb..4bd4f32bcdab 100644
> > > --- a/drivers/misc/eeprom/at24.c
> > > +++ b/drivers/misc/eeprom/at24.c
> > > @@ -758,15 +758,6 @@ static int at24_probe(struct i2c_client *client)
> > >         }
> > >         pm_runtime_enable(dev);
> > >
> > > -       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> > > -       if (IS_ERR(at24->nvmem)) {
> > > -               pm_runtime_disable(dev);
> > > -               if (!pm_runtime_status_suspended(dev))
> > > -                       regulator_disable(at24->vcc_reg);
> > > -               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> > > -                                    "failed to register nvmem\n");
> > > -       }
> > > -
> > >         /*
> > >          * Perform a one-byte test read to verify that the chip is functional,
> > >          * unless powering on the device is to be avoided during probe (i.e.
> > > @@ -782,6 +773,15 @@ static int at24_probe(struct i2c_client *client)
> > >                 }
> > >         }
> > >
> > > +       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> > > +       if (IS_ERR(at24->nvmem)) {
> > > +               pm_runtime_disable(dev);
> > > +               if (!pm_runtime_status_suspended(dev))
> > > +                       regulator_disable(at24->vcc_reg);
> > > +               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> > > +                                    "failed to register nvmem\n");
> > > +       }
> > > +
> > >         /* If this a SPD EEPROM, probe for DDR3 thermal sensor */
> > >         if (cdata == &at24_data_spd)
> > >                 at24_probe_temp_sensor(client);
> > > --
> > > 2.44.0.683.g7961c838ac-goog
> > >
> >
> > Looks good, can you add a Fixes tag?
> >
> > Thanks,
> > Bartosz
>
> Wait... While the patch is still correct - we shouldn't needlessly
> create the nvmem device - why would anything crash? Looks like a
> problem with nvmem then? How did you trigger this issue?
>
> Bart

Re: [PATCH v1] at24: fix memory corruption race condition

Posted by Bartosz Golaszewski 1 week, 5 days ago

On Thu, Apr 18, 2024 at 7:13 PM Daniel Okazaki <dtokazaki@google.com> wrote:
>
> nvmem devices allow for linking by name in the DTS which doesn't
> create a dependency in the probe order.
>
> What happens is driver B probe starts shortly after the eeprom
> probe and calls of_nvmem_device_get. Since a device is
> registered it starts using it; however if the eeprom isn't there
> then the read will fail and it will start tearing down the resources.
> Driver B will now access invalid memory causing a kernel panic.
>
> Daniel
>

Please don't top-post on the linux kernel mailing list.

I'm Cc'ing Srini, the maintainer of NVMEM. I think this is an issue
with nvmem core as it shouldn't allow access to nvmem devices once it
starts tearing them down. Srini, could you comment on this?

Bartosz

>
> On Wed, Apr 17, 2024 at 5:23 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> >
> > On Thu, Apr 18, 2024 at 1:59 AM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> > >
> > > On Thu, Apr 18, 2024 at 1:07 AM Daniel Okazaki <dtokazaki@google.com> wrote:
> > > >
> > > > If the eeprom is not accessible, an nvmem device will be registered, the
> > > > read will fail, and the device will be torn down. If another driver
> > > > accesses the nvmem device after the teardown, it will reference
> > > > invalid memory.
> > > >
> > > > Move the failure point before registering the nvmem device.
> > > >
> > > > Signed-off-by: Daniel Okazaki <dtokazaki@google.com>
> > > > ---
> > > >  drivers/misc/eeprom/at24.c | 18 +++++++++---------
> > > >  1 file changed, 9 insertions(+), 9 deletions(-)
> > > >
> > > > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> > > > index 572333ead5fb..4bd4f32bcdab 100644
> > > > --- a/drivers/misc/eeprom/at24.c
> > > > +++ b/drivers/misc/eeprom/at24.c
> > > > @@ -758,15 +758,6 @@ static int at24_probe(struct i2c_client *client)
> > > >         }
> > > >         pm_runtime_enable(dev);
> > > >
> > > > -       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> > > > -       if (IS_ERR(at24->nvmem)) {
> > > > -               pm_runtime_disable(dev);
> > > > -               if (!pm_runtime_status_suspended(dev))
> > > > -                       regulator_disable(at24->vcc_reg);
> > > > -               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> > > > -                                    "failed to register nvmem\n");
> > > > -       }
> > > > -
> > > >         /*
> > > >          * Perform a one-byte test read to verify that the chip is functional,
> > > >          * unless powering on the device is to be avoided during probe (i.e.
> > > > @@ -782,6 +773,15 @@ static int at24_probe(struct i2c_client *client)
> > > >                 }
> > > >         }
> > > >
> > > > +       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> > > > +       if (IS_ERR(at24->nvmem)) {
> > > > +               pm_runtime_disable(dev);
> > > > +               if (!pm_runtime_status_suspended(dev))
> > > > +                       regulator_disable(at24->vcc_reg);
> > > > +               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> > > > +                                    "failed to register nvmem\n");
> > > > +       }
> > > > +
> > > >         /* If this a SPD EEPROM, probe for DDR3 thermal sensor */
> > > >         if (cdata == &at24_data_spd)
> > > >                 at24_probe_temp_sensor(client);
> > > > --
> > > > 2.44.0.683.g7961c838ac-goog
> > > >
> > >
> > > Looks good, can you add a Fixes tag?
> > >
> > > Thanks,
> > > Bartosz
> >
> > Wait... While the patch is still correct - we shouldn't needlessly
> > create the nvmem device - why would anything crash? Looks like a
> > problem with nvmem then? How did you trigger this issue?
> >
> > Bart

[PATCH v2] eeprom: at24: fix memory corruption race condition

Posted by Daniel Okazaki 1 week, 4 days ago

If the eeprom is not accessible, an nvmem device will be registered, the
read will fail, and the device will be torn down. If another driver
accesses the nvmem device after the teardown, it will reference
invalid memory.

Move the failure point before registering the nvmem device.

Signed-off-by: Daniel Okazaki <dtokazaki@google.com>
Fixes: b20eb4c1 ("eeprom: at24: drop unnecessary label")
---
 drivers/misc/eeprom/at24.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 572333ead5fb..4bd4f32bcdab 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -758,15 +758,6 @@ static int at24_probe(struct i2c_client *client)
 	}
 	pm_runtime_enable(dev);
 
-	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
-	if (IS_ERR(at24->nvmem)) {
-		pm_runtime_disable(dev);
-		if (!pm_runtime_status_suspended(dev))
-			regulator_disable(at24->vcc_reg);
-		return dev_err_probe(dev, PTR_ERR(at24->nvmem),
-				     "failed to register nvmem\n");
-	}
-
 	/*
 	 * Perform a one-byte test read to verify that the chip is functional,
 	 * unless powering on the device is to be avoided during probe (i.e.
@@ -782,6 +773,15 @@ static int at24_probe(struct i2c_client *client)
 		}
 	}
 
+	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
+	if (IS_ERR(at24->nvmem)) {
+		pm_runtime_disable(dev);
+		if (!pm_runtime_status_suspended(dev))
+			regulator_disable(at24->vcc_reg);
+		return dev_err_probe(dev, PTR_ERR(at24->nvmem),
+				     "failed to register nvmem\n");
+	}
+
 	/* If this a SPD EEPROM, probe for DDR3 thermal sensor */
 	if (cdata == &at24_data_spd)
 		at24_probe_temp_sensor(client);
-- 
2.44.0.769.g3c40516874-goog

Re: [PATCH v2] eeprom: at24: fix memory corruption race condition

Posted by Markus Elfring 1 week, 4 days ago

…
> Move the failure point before registering the nvmem device.
…
> Fixes: b20eb4c1 ("eeprom: at24: drop unnecessary label")

Please use a longer hash for this tag.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.9-rc4#n145

Regards,
Markus

[PATCH v3] eeprom: at24: fix memory corruption race condition

Posted by Daniel Okazaki 1 week, 4 days ago

If the eeprom is not accessible, an nvmem device will be registered, the
read will fail, and the device will be torn down. If another driver
accesses the nvmem device after the teardown, it will reference
invalid memory.

Move the failure point before registering the nvmem device.

Signed-off-by: Daniel Okazaki <dtokazaki@google.com>
Fixes: b20eb4c1f026 ("eeprom: at24: drop unnecessary label")
---
 drivers/misc/eeprom/at24.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index 572333ead5fb..4bd4f32bcdab 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -758,15 +758,6 @@ static int at24_probe(struct i2c_client *client)
 	}
 	pm_runtime_enable(dev);
 
-	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
-	if (IS_ERR(at24->nvmem)) {
-		pm_runtime_disable(dev);
-		if (!pm_runtime_status_suspended(dev))
-			regulator_disable(at24->vcc_reg);
-		return dev_err_probe(dev, PTR_ERR(at24->nvmem),
-				     "failed to register nvmem\n");
-	}
-
 	/*
 	 * Perform a one-byte test read to verify that the chip is functional,
 	 * unless powering on the device is to be avoided during probe (i.e.
@@ -782,6 +773,15 @@ static int at24_probe(struct i2c_client *client)
 		}
 	}
 
+	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
+	if (IS_ERR(at24->nvmem)) {
+		pm_runtime_disable(dev);
+		if (!pm_runtime_status_suspended(dev))
+			regulator_disable(at24->vcc_reg);
+		return dev_err_probe(dev, PTR_ERR(at24->nvmem),
+				     "failed to register nvmem\n");
+	}
+
 	/* If this a SPD EEPROM, probe for DDR3 thermal sensor */
 	if (cdata == &at24_data_spd)
 		at24_probe_temp_sensor(client);
-- 
2.44.0.769.g3c40516874-goog

Re: [PATCH v3] eeprom: at24: fix memory corruption race condition

Posted by Markus Elfring 1 week, 3 days ago

> If the eeprom is not accessible, an nvmem device will be registered, the
> read will fail, and the device will be torn down.
…

Can it be nicer to present the introduction for failure conditions as an enumeration?


> Move the failure point before registering the nvmem device.
…

I would interpret the diff data more in the way that a devm_nvmem_register() call
should be performed a bit later in the implementation of the function “at24_probe”.
How do you think about to mention the affected function also in the summary phrase?


> ---
…

Please add a version description for your change approach.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst?h=v6.9-rc4#n713

Regards,
Markus

Re: [PATCH v3] eeprom: at24: fix memory corruption race condition

Posted by Greg Kroah-Hartman 1 week, 3 days ago

On Sat, Apr 20, 2024 at 11:11:05AM +0200, Markus Elfring wrote:
> > If the eeprom is not accessible, an nvmem device will be registered, the
> > read will fail, and the device will be torn down.
> …
> 
> Can it be nicer to present the introduction for failure conditions as an enumeration?
> 
> 
> > Move the failure point before registering the nvmem device.
> …
> 
> I would interpret the diff data more in the way that a devm_nvmem_register() call
> should be performed a bit later in the implementation of the function “at24_probe”.
> How do you think about to mention the affected function also in the summary phrase?
> 

Hi,

This is the semi-friendly patch-bot of Greg Kroah-Hartman.

Markus, you seem to have sent a nonsensical or otherwise pointless
review comment to a patch submission on a Linux kernel developer mailing
list.  I strongly suggest that you not do this anymore.  Please do not
bother developers who are actively working to produce patches and
features with comments that, in the end, are a waste of time.

Patch submitter, please ignore Markus's suggestion; you do not need to
follow it at all.  The person/bot/AI that sent it is being ignored by
almost all Linux kernel maintainers for having a persistent pattern of
behavior of producing distracting and pointless commentary, and
inability to adapt to feedback.  Please feel free to also ignore emails
from them.

thanks,

greg k-h's patch email bot

Re: [PATCH v3] eeprom: at24: fix memory corruption race condition

Posted by Greg Kroah-Hartman 1 week, 3 days ago

On Fri, Apr 19, 2024 at 07:12:00PM +0000, Daniel Okazaki wrote:
> If the eeprom is not accessible, an nvmem device will be registered, the
> read will fail, and the device will be torn down. If another driver
> accesses the nvmem device after the teardown, it will reference
> invalid memory.
> 
> Move the failure point before registering the nvmem device.
> 
> Signed-off-by: Daniel Okazaki <dtokazaki@google.com>
> Fixes: b20eb4c1f026 ("eeprom: at24: drop unnecessary label")
> ---
>  drivers/misc/eeprom/at24.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 572333ead5fb..4bd4f32bcdab 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -758,15 +758,6 @@ static int at24_probe(struct i2c_client *client)
>  	}
>  	pm_runtime_enable(dev);
>  
> -	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> -	if (IS_ERR(at24->nvmem)) {
> -		pm_runtime_disable(dev);
> -		if (!pm_runtime_status_suspended(dev))
> -			regulator_disable(at24->vcc_reg);
> -		return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> -				     "failed to register nvmem\n");
> -	}
> -
>  	/*
>  	 * Perform a one-byte test read to verify that the chip is functional,
>  	 * unless powering on the device is to be avoided during probe (i.e.
> @@ -782,6 +773,15 @@ static int at24_probe(struct i2c_client *client)
>  		}
>  	}
>  
> +	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> +	if (IS_ERR(at24->nvmem)) {
> +		pm_runtime_disable(dev);
> +		if (!pm_runtime_status_suspended(dev))
> +			regulator_disable(at24->vcc_reg);
> +		return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> +				     "failed to register nvmem\n");
> +	}
> +
>  	/* If this a SPD EEPROM, probe for DDR3 thermal sensor */
>  	if (cdata == &at24_data_spd)
>  		at24_probe_temp_sensor(client);
> -- 
> 2.44.0.769.g3c40516874-goog
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- This looks like a new version of a previously submitted patch, but you
  did not list below the --- line any changes from the previous version.
  Please read the section entitled "The canonical patch format" in the
  kernel file, Documentation/process/submitting-patches.rst for what
  needs to be done here to properly describe this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

Re: [PATCH v1] at24: fix memory corruption race condition

Posted by Daniel Okazaki 1 week, 5 days ago

Sorry forgot to include the key being that the probes happen in
parallel so there are race conditions to the registering of the
nvmem and other drivers using it after it starts getting torn down
and memory gets freed.

On Thu, Apr 18, 2024 at 10:13 AM Daniel Okazaki <dtokazaki@google.com> wrote:
>
> nvmem devices allow for linking by name in the DTS which doesn't
> create a dependency in the probe order.
>
> What happens is driver B probe starts shortly after the eeprom
> probe and calls of_nvmem_device_get. Since a device is
> registered it starts using it; however if the eeprom isn't there
> then the read will fail and it will start tearing down the resources.
> Driver B will now access invalid memory causing a kernel panic.
>
> Daniel
>
>
> On Wed, Apr 17, 2024 at 5:23 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> >
> > On Thu, Apr 18, 2024 at 1:59 AM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> > >
> > > On Thu, Apr 18, 2024 at 1:07 AM Daniel Okazaki <dtokazaki@google.com> wrote:
> > > >
> > > > If the eeprom is not accessible, an nvmem device will be registered, the
> > > > read will fail, and the device will be torn down. If another driver
> > > > accesses the nvmem device after the teardown, it will reference
> > > > invalid memory.
> > > >
> > > > Move the failure point before registering the nvmem device.
> > > >
> > > > Signed-off-by: Daniel Okazaki <dtokazaki@google.com>
> > > > ---
> > > >  drivers/misc/eeprom/at24.c | 18 +++++++++---------
> > > >  1 file changed, 9 insertions(+), 9 deletions(-)
> > > >
> > > > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> > > > index 572333ead5fb..4bd4f32bcdab 100644
> > > > --- a/drivers/misc/eeprom/at24.c
> > > > +++ b/drivers/misc/eeprom/at24.c
> > > > @@ -758,15 +758,6 @@ static int at24_probe(struct i2c_client *client)
> > > >         }
> > > >         pm_runtime_enable(dev);
> > > >
> > > > -       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> > > > -       if (IS_ERR(at24->nvmem)) {
> > > > -               pm_runtime_disable(dev);
> > > > -               if (!pm_runtime_status_suspended(dev))
> > > > -                       regulator_disable(at24->vcc_reg);
> > > > -               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> > > > -                                    "failed to register nvmem\n");
> > > > -       }
> > > > -
> > > >         /*
> > > >          * Perform a one-byte test read to verify that the chip is functional,
> > > >          * unless powering on the device is to be avoided during probe (i.e.
> > > > @@ -782,6 +773,15 @@ static int at24_probe(struct i2c_client *client)
> > > >                 }
> > > >         }
> > > >
> > > > +       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> > > > +       if (IS_ERR(at24->nvmem)) {
> > > > +               pm_runtime_disable(dev);
> > > > +               if (!pm_runtime_status_suspended(dev))
> > > > +                       regulator_disable(at24->vcc_reg);
> > > > +               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> > > > +                                    "failed to register nvmem\n");
> > > > +       }
> > > > +
> > > >         /* If this a SPD EEPROM, probe for DDR3 thermal sensor */
> > > >         if (cdata == &at24_data_spd)
> > > >                 at24_probe_temp_sensor(client);
> > > > --
> > > > 2.44.0.683.g7961c838ac-goog
> > > >
> > >
> > > Looks good, can you add a Fixes tag?
> > >
> > > Thanks,
> > > Bartosz
> >
> > Wait... While the patch is still correct - we shouldn't needlessly
> > create the nvmem device - why would anything crash? Looks like a
> > problem with nvmem then? How did you trigger this issue?
> >
> > Bart