Add two parameter to specify how many times a kexec kernel can be loaded.

These parameter allow hardening the system.

While we are at it, fix a documentation issue and refactor some code.

To: Jonathan Corbet <corbet@lwn.net>
To: Eric Biederman <ebiederm@xmission.com>
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: kexec@lists.infradead.org
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ross Zwisler <zwisler@kernel.org>
To: Philipp Rudo <prudo@redhat.com>
To: Guilherme G. Piccoli <gpiccoli@igalia.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Petr Tesarik <petr@tesarici.cz>
Cc: Baoquan He <bhe@redhat.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>

---
Changes in v6:
- Fix kexec type on kexec_file
- Match the length of the table borders to the sections underline (Thanks Bagas!)
- Fix typo on kexec_load_limit_reboot (Thanks Petr!)
- Improve commit message (Thanks Baoquan!)
- Link to v5: https://lore.kernel.org/r/20221114-disable-kexec-reset-v5-0-1bd37caf3c75@chromium.org

Changes in v5:
- Remove maxlen from ctl_table. Thanks Steven!
- Link to v4: https://lore.kernel.org/r/20221114-disable-kexec-reset-v4-0-ab809c8d988c@chromium.org

Changes in v4 (Thanks Steven!):
- Uses sysctl instead or module_parameters
- Pass image type instead of boolean to permitted
- Fix typo on flag handling
- Return -EINVAL for values that does not change the current value.
- Link to v3: https://lore.kernel.org/r/20221114-disable-kexec-reset-v3-0-4ef4e929adf6@chromium.org

Changes in v3:
- s/paramter/parameter/ Thanks Ghilherme!
- s/permited/permitted/ Thanks Joel!
- Link to v2: https://lore.kernel.org/r/20221114-disable-kexec-reset-v2-0-c498313c1bb5@chromium.org

Changes in v2:
- Instead of kexec_reboot_disabled, add two new counters (Thanks Philipp!)
- Link to v1: https://lore.kernel.org/r/20221114-disable-kexec-reset-v1-0-fb51d20cf871@chromium.org

---
Ricardo Ribalda (3):
      Documentation: sysctl: Correct kexec_load_disabled
      kexec: Factor out kexec_load_permitted
      kexec: Introduce sysctl parameters kexec_load_limit_*

 Documentation/admin-guide/sysctl/kernel.rst | 25 +++++++-
 include/linux/kexec.h                       |  3 +-
 kernel/kexec.c                              |  4 +-
 kernel/kexec_core.c                         | 94 ++++++++++++++++++++++++++++-
 kernel/kexec_file.c                         | 11 ++--
 5 files changed, 127 insertions(+), 10 deletions(-)
---
base-commit: 479174d402bcf60789106eedc4def3957c060bad
change-id: 20221114-disable-kexec-reset-19b7e117338f

Best regards,
-- 
Ricardo Ribalda <ribalda@chromium.org>

On 01/04/23 at 03:38pm, Ricardo Ribalda wrote:
> Add two parameter to specify how many times a kexec kernel can be loaded.
> 
> These parameter allow hardening the system.
> 
> While we are at it, fix a documentation issue and refactor some code.

The whole series looks good to me, thx.

Acked-by: Baoquan He <bhe@redhat.com>

> 
> To: Jonathan Corbet <corbet@lwn.net>
> To: Eric Biederman <ebiederm@xmission.com>
> Cc: linux-doc@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: kexec@lists.infradead.org
> Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
> Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ross Zwisler <zwisler@kernel.org>
> To: Philipp Rudo <prudo@redhat.com>
> To: Guilherme G. Piccoli <gpiccoli@igalia.com>
> Cc: Bagas Sanjaya <bagasdotme@gmail.com>
> Cc: Petr Tesarik <petr@tesarici.cz>
> Cc: Baoquan He <bhe@redhat.com>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> 
> ---
> Changes in v6:
> - Fix kexec type on kexec_file
> - Match the length of the table borders to the sections underline (Thanks Bagas!)
> - Fix typo on kexec_load_limit_reboot (Thanks Petr!)
> - Improve commit message (Thanks Baoquan!)
> - Link to v5: https://lore.kernel.org/r/20221114-disable-kexec-reset-v5-0-1bd37caf3c75@chromium.org
> 
> Changes in v5:
> - Remove maxlen from ctl_table. Thanks Steven!
> - Link to v4: https://lore.kernel.org/r/20221114-disable-kexec-reset-v4-0-ab809c8d988c@chromium.org
> 
> Changes in v4 (Thanks Steven!):
> - Uses sysctl instead or module_parameters
> - Pass image type instead of boolean to permitted
> - Fix typo on flag handling
> - Return -EINVAL for values that does not change the current value.
> - Link to v3: https://lore.kernel.org/r/20221114-disable-kexec-reset-v3-0-4ef4e929adf6@chromium.org
> 
> Changes in v3:
> - s/paramter/parameter/ Thanks Ghilherme!
> - s/permited/permitted/ Thanks Joel!
> - Link to v2: https://lore.kernel.org/r/20221114-disable-kexec-reset-v2-0-c498313c1bb5@chromium.org
> 
> Changes in v2:
> - Instead of kexec_reboot_disabled, add two new counters (Thanks Philipp!)
> - Link to v1: https://lore.kernel.org/r/20221114-disable-kexec-reset-v1-0-fb51d20cf871@chromium.org
> 
> ---
> Ricardo Ribalda (3):
>       Documentation: sysctl: Correct kexec_load_disabled
>       kexec: Factor out kexec_load_permitted
>       kexec: Introduce sysctl parameters kexec_load_limit_*
> 
>  Documentation/admin-guide/sysctl/kernel.rst | 25 +++++++-
>  include/linux/kexec.h                       |  3 +-
>  kernel/kexec.c                              |  4 +-
>  kernel/kexec_core.c                         | 94 ++++++++++++++++++++++++++++-
>  kernel/kexec_file.c                         | 11 ++--
>  5 files changed, 127 insertions(+), 10 deletions(-)
> ---
> base-commit: 479174d402bcf60789106eedc4def3957c060bad
> change-id: 20221114-disable-kexec-reset-19b7e117338f
> 
> Best regards,
> -- 
> Ricardo Ribalda <ribalda@chromium.org>
>