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

Bartosz Golaszewski
2024-04-18T00:23:50Z

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