Re: [PATCH v2] nvmem: core: Set no-read-write provider to avoid userspace read/write

[Gaurav Kohli]

On 3/22/2019 11:42 PM, Gaurav Kohli wrote:
> Hi Srinivas,
>
> Thanks for the patch, Something like this only i have tested in the 
> morning, instead of unused, i have put dev group inside config as well.
>
> We will test the exact patch and update the same.
>
> Regards
>
> Gaurav
>
> On 3/22/2019 8:32 PM, Srinivas Kandagatla wrote:
> > On 20/03/2019 17:50, Gaurav Kohli wrote:
> > > > Is root only option not helping you in this case?
> > > Yes we want to protect at root level as well, i mean it is better if 
> > > we can avoid exposing to userspace at all.
> > Can you try below patch!
Hi Srinivas,

Thanks for the patch.

I have checked the patch and also tested the same , and it is working as 
expected(no creation of nvmem sysfs)

Applied with some conflict on line 41.

Reviewed-by: Gaurav Kohli <gkohli@xxxxxxxxxxxxxx>
Tested-by: Gaurav Kohli <gkohli@xxxxxxxxxxxxxx>

Regards

Gaurav


> > > > We could go down the route of adding new config option something 
> > > > like CONFIG_NVMEM_NO_SYSFS_ENTRY to prevent adding nvmem entry in 
> > > > userspace.
> > > >
> > > > Let me know if you are happy to create a patch for this change?
> > >
> > > I am happy with either way config option or dt binding(seems easy), 
> > > please let me know we will post new patch for the same.
> > DT way is totally NAK.
> >
> >
> > --------------------------->cut<-----------------------------------
> >
> > From: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> > Date: Wed, 20 Mar 2019 16:15:21 +0000
> > Subject: [PATCH] nvmem: core: add support to NVMEM_NO_SYSFS_ENTRY
> >
> > Some users might not want to expose nvmem entry to sysfs and
> > only intend to use kernel interface so add such provision.
> >
> > Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
> > ---
> > ÂDocumentation/ABI/stable/sysfs-bus-nvmem |Â 2 ++
> > Âdrivers/nvmem/KconfigÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ |Â 5 +++++
> > Âdrivers/nvmem/core.cÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ | 11 ++++++-----
> > Â3 files changed, 13 insertions(+), 5 deletions(-)
> >
> > diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem 
> > b/Documentation/ABI/stable/sysfs-bus-nvmem
> > index 5923ab4620c5..12aab0a85fea 100644
> > --- a/Documentation/ABI/stable/sysfs-bus-nvmem
> > +++ b/Documentation/ABI/stable/sysfs-bus-nvmem
> > @@ -6,6 +6,8 @@ Description:
> > ÂÂÂÂÂÂÂÂ This file allows user to read/write the raw NVMEM contents.
> > ÂÂÂÂÂÂÂÂ Permissions for write to this file depends on the nvmem
> > ÂÂÂÂÂÂÂÂ provider configuration.
> > +ÂÂÂÂÂÂÂ Note: This file is not present if CONFIG_NVMEM_NO_SYSFS_ENTRY
> > +ÂÂÂÂÂÂÂ is enabled
> >
> > ÂÂÂÂÂÂÂÂ ex:
> > ÂÂÂÂÂÂÂÂ hexdump /sys/bus/nvmem/devices/qfprom0/nvmem
> > diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> > index 0a7a470ee859..6ab3276d287c 100644
> > --- a/drivers/nvmem/Kconfig
> > +++ b/drivers/nvmem/Kconfig
> > @@ -192,4 +192,9 @@ config SC27XX_EFUSE
> > ÂÂÂÂÂÂ This driver can also be built as a module. If so, the module
> > ÂÂÂÂÂÂ will be called nvmem-sc27xx-efuse.
> >
> > +config NVMEM_NO_SYSFS_ENTRY
> > +ÂÂÂ bool "No nvmem sysfs entry"
> > +
> > +ÂÂÂ help
> > +ÂÂÂÂÂÂÂ Say Yes if you do not want to add nvmem entry to sysfs.
> > Âendif
> > diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> > index b9a0270883a0..c70f183fe379 100644
> > --- a/drivers/nvmem/core.c
> > +++ b/drivers/nvmem/core.c
> > @@ -216,7 +216,7 @@ static const struct attribute_group 
> > nvmem_bin_rw_group = {
> > ÂÂÂÂ .attrsÂÂÂÂÂÂÂ = nvmem_attrs,
> > Â};
> >
> > -static const struct attribute_group *nvmem_rw_dev_groups[] = {
> > +static const __maybe_unused struct attribute_group 
> > *nvmem_rw_dev_groups[] = {
> > ÂÂÂÂ &nvmem_bin_rw_group,
> > ÂÂÂÂ NULL,
> > Â};
> > @@ -240,7 +240,7 @@ static const struct attribute_group 
> > nvmem_bin_ro_group = {
> > ÂÂÂÂ .attrsÂÂÂÂÂÂÂ = nvmem_attrs,
> > Â};
> >
> > -static const struct attribute_group *nvmem_ro_dev_groups[] = {
> > +static const __maybe_unused struct attribute_group 
> > *nvmem_ro_dev_groups[] = {
> > ÂÂÂÂ &nvmem_bin_ro_group,
> > ÂÂÂÂ NULL,
> > Â};
> > @@ -265,7 +265,7 @@ static const struct attribute_group 
> > nvmem_bin_rw_root_group = {
> > ÂÂÂÂ .attrsÂÂÂÂÂÂÂ = nvmem_attrs,
> > Â};
> >
> > -static const struct attribute_group *nvmem_rw_root_dev_groups[] = {
> > +static const __maybe_unused struct attribute_group 
> > *nvmem_rw_root_dev_groups[] = {
> > ÂÂÂÂ &nvmem_bin_rw_root_group,
> > ÂÂÂÂ NULL,
> > Â};
> > @@ -289,7 +289,7 @@ static const struct attribute_group 
> > nvmem_bin_ro_root_group = {
> > ÂÂÂÂ .attrsÂÂÂÂÂÂÂ = nvmem_attrs,
> > Â};
> >
> > -static const struct attribute_group *nvmem_ro_root_dev_groups[] = {
> > +static const __maybe_unused struct attribute_group 
> > *nvmem_ro_root_dev_groups[] = {
> > ÂÂÂÂ &nvmem_bin_ro_root_group,
> > ÂÂÂÂ NULL,
> > Â};
> > @@ -688,6 +688,7 @@ struct nvmem_device *nvmem_register(const struct 
> > nvmem_config *config)
> > ÂÂÂÂ nvmem->read_only = device_property_present(config->dev, 
> > "read-only") |
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ config->read_only;
> >
> > +#if !defined(CONFIG_NVMEM_NO_SYSFS_ENTRY)
> > ÂÂÂÂ if (config->root_only)
> > ÂÂÂÂÂÂÂÂ nvmem->dev.groups = nvmem->read_only ?
> > ÂÂÂÂÂÂÂÂÂÂÂÂ nvmem_ro_root_dev_groups :
> > @@ -696,7 +697,7 @@ struct nvmem_device *nvmem_register(const struct 
> > nvmem_config *config)
> > ÂÂÂÂÂÂÂÂ nvmem->dev.groups = nvmem->read_only ?
> > ÂÂÂÂÂÂÂÂÂÂÂÂ nvmem_ro_dev_groups :
> > ÂÂÂÂÂÂÂÂÂÂÂÂ nvmem_rw_dev_groups;
> > -
> > +#endif
> > ÂÂÂÂ device_initialize(&nvmem->dev);
> >
> > ÂÂÂÂ dev_dbg(&nvmem->dev, "Registering nvmem device %s\n", 
> > config->name);
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center,
Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.