On Tue, Jun 14, 2022 at 09:45:42PM +0200, Wolfram Sang wrote: > Hi Michał, > > I finally had a look at your patch... > > > put_device(&adap->dev) might free the memory pointed to by `adap`, > > so we shouldn't read adap->owner after that. > > > > Fix by saving module pointer before calling put_device(). > > ... and found a different approach for this problem from 2019: > > http://patchwork.ozlabs.org/project/linux-i2c/patch/1577439272-10362-1-git-send-email-vulab@xxxxxxxxxxx/ > > I think this is also proper. I found other subsystems in the kernel > first putting the module, then the device. Do you see problems with the > above patch? > > Thanks for looking into the issue! Hi! I looked briefly at the kobject machinery and it seems to ignore module dependencies. So while both approaches might work, I'd usually reverse the order the init code is using: in this case module_get+device_get, so on release: device_put+module_put. I don't know what keeps the kernel from unloading the module after module_put() and before the function returns, but I assume that would blow up for both patches. Best Regards Michał Mirosław > > > > Signed-off-by: Michał Mirosław <mirq-linux@xxxxxxxxxxxx> > > --- > > drivers/i2c/i2c-core-base.c | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c > > index 2c59dd748a49..5d694f8ce9ef 100644 > > --- a/drivers/i2c/i2c-core-base.c > > +++ b/drivers/i2c/i2c-core-base.c > > @@ -2464,11 +2464,14 @@ EXPORT_SYMBOL(i2c_get_adapter); > > > > void i2c_put_adapter(struct i2c_adapter *adap) > > { > > + struct module *owner; > > + > > if (!adap) > > return; > > > > + owner = adap->owner; > > put_device(&adap->dev); > > - module_put(adap->owner); > > + module_put(owner); > > } > > EXPORT_SYMBOL(i2c_put_adapter); > > > > -- > > 2.30.2 > > -- Michał Mirosław
