struct bin_attribute contains a bunch of pointer members, which when
overwritten by accident or malice can lead to system instability and
security problems.
Moving the definitions of struct bin_attribute to read-only memory
makes these modifications impossible.
The same change has been performed for many other structures in the
past. (struct class, struct ctl_table...)

For the structure definitions throughout the core to be moved to
read-only memory the following steps are necessary.

1) Change all callbacks invoked from the sysfs core to only pass const
   pointers
2) Adapt the sysfs core to only work in terms of const pointers
3) Adapt the sysfs core APIs to allow const pointers
4) Change all structure definitions through the core to const

This series provides the foundation for step 1) above.
It converts some callbacks in a single step to const and provides a
foundation for those callbacks where a single step is not possible.

Patches 1-5 change the bin_attribute callbacks of 'struct
attribute_group'. The remaining ones touch 'struct bin_attribute' itself.

The techniques employed by this series can later be reused for the
same change for other sysfs attributes.

This series is intended to be merged through the driver core tree.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
Changes in v2:
- Drop RFC state
- Refuse registration of attributes with both read/read_new or
  write/write_new
- Remove don't drop llseek() callback, as it is actually used.
  Instead also migrate it to "const".
- _Generic machinery: Simplify and make more robust against misuse
- Link to v1: https://lore.kernel.org/r/20241031-sysfs-const-bin_attr-v1-0-2281afa7f055@weissschuh.net

---
Thomas Weißschuh (10):
      sysfs: explicitly pass size to sysfs_add_bin_file_mode_ns()
      sysfs: introduce callback attribute_group::bin_size
      PCI/sysfs: Calculate bin_attribute size through bin_size()
      nvmem: core: calculate bin_attribute size through bin_size()
      sysfs: treewide: constify attribute callback of bin_is_visible()
      sysfs: treewide: constify attribute callback of bin_attribute::mmap()
      sysfs: treewide: constify attribute callback of bin_attribute::llseek()
      sysfs: implement all BIN_ATTR_* macros in terms of __BIN_ATTR()
      sysfs: bin_attribute: add const read/write callback variants
      driver core: Constify attribute arguments of binary attributes

 arch/alpha/kernel/pci-sysfs.c           |  6 +--
 drivers/base/node.c                     |  4 +-
 drivers/base/topology.c                 |  4 +-
 drivers/cxl/port.c                      |  2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_psp.c |  2 +-
 drivers/infiniband/hw/qib/qib_sysfs.c   |  2 +-
 drivers/misc/ocxl/sysfs.c               |  2 +-
 drivers/mtd/spi-nor/sysfs.c             |  2 +-
 drivers/nvmem/core.c                    | 16 ++++--
 drivers/pci/p2pdma.c                    |  2 +-
 drivers/pci/pci-sysfs.c                 | 42 ++++++++-------
 drivers/pci/vpd.c                       |  2 +-
 drivers/platform/x86/amd/hsmp.c         |  2 +-
 drivers/platform/x86/intel/pmt/class.c  |  2 +-
 drivers/platform/x86/intel/sdsi.c       |  2 +-
 drivers/scsi/scsi_sysfs.c               |  2 +-
 drivers/uio/uio_hv_generic.c            |  2 +-
 drivers/usb/core/sysfs.c                |  2 +-
 fs/sysfs/file.c                         | 30 +++++++----
 fs/sysfs/group.c                        |  5 +-
 fs/sysfs/sysfs.h                        |  2 +-
 include/linux/sysfs.h                   | 94 ++++++++++++++++++++-------------
 22 files changed, 138 insertions(+), 91 deletions(-)
---
base-commit: 3e5e6c9900c3d71895e8bdeacfb579462e98eba1
change-id: 20241028-sysfs-const-bin_attr-a00896481d0b

Best regards,
-- 
Thomas Weißschuh <linux@weissschuh.net>

Hello,

> struct bin_attribute contains a bunch of pointer members, which when
> overwritten by accident or malice can lead to system instability and
> security problems.
> Moving the definitions of struct bin_attribute to read-only memory
> makes these modifications impossible.
> The same change has been performed for many other structures in the
> past. (struct class, struct ctl_table...)
> 
> For the structure definitions throughout the core to be moved to
> read-only memory the following steps are necessary.
> 
> 1) Change all callbacks invoked from the sysfs core to only pass const
>    pointers
> 2) Adapt the sysfs core to only work in terms of const pointers
> 3) Adapt the sysfs core APIs to allow const pointers
> 4) Change all structure definitions through the core to const
> 
> This series provides the foundation for step 1) above.
> It converts some callbacks in a single step to const and provides a
> foundation for those callbacks where a single step is not possible.
> 
> Patches 1-5 change the bin_attribute callbacks of 'struct
> attribute_group'. The remaining ones touch 'struct bin_attribute' itself.
> 
> The techniques employed by this series can later be reused for the
> same change for other sysfs attributes.
> 
> This series is intended to be merged through the driver core tree.

This is very nice.  Thank you!

For PCI changes:
  Acked-by: Krzysztof Wilczyński <kw@linux.com>

This reminded me of an old discussions with Greg and Bjorn about how to set
size correctly for our ROM and BAR sysfs objects.  Nice to see a very nice
approach here, indeed.

	Krzysztof

On Sun, Nov 03, 2024 at 05:03:29PM +0000, Thomas Weißschuh wrote:
> struct bin_attribute contains a bunch of pointer members, which when
> overwritten by accident or malice can lead to system instability and
> security problems.
> Moving the definitions of struct bin_attribute to read-only memory
> makes these modifications impossible.
> The same change has been performed for many other structures in the
> past. (struct class, struct ctl_table...)

Throughout series, it would be more readable if you added blank lines
between paragraphs.