Re: [PATCH v2] lsm: constify the 'target' parameter in security_capget()

[Paul Moore]

On Mon, Aug 7, 2023 at 2:59 AM Khadija Kamran <kamrankhadijadj@xxxxxxxxx> wrote:
>
> Three LSMs register the implementations for the "capget" hook: AppArmor,
> SELinux, and the normal capability code. Looking at the function
> implementations we may observe that the first parameter "target" is not
> changing.
>
> Mark the first argument "target" of LSM hook security_capget() as
> "const" since it will not be changing in the LSM hook.
>
> cap_capget() LSM hook declaration exceeds the 80 characters per line
> limit. Split the function declaration to multple lines to decrease the

"multiple" :)

Don't worry, I'll fix that in the merge.

There is one more nitpick below, but I think this looks good.  I'll
give this a few days to see if John can ACK the AppArmor bits, but if
we don't hear from him by mid-week I'll plan to merge this.

Thanks!

> line length.
>
> Signed-off-by: Khadija Kamran <kamrankhadijadj@xxxxxxxxx>
> ---
> Changes in v2:
>  - Squash the patches 1/2 and 2/2 into a single patch
>  - Simplify the commit message
>
>  include/linux/lsm_hook_defs.h | 2 +-
>  include/linux/security.h      | 7 ++++---
>  kernel/capability.c           | 2 +-
>  security/apparmor/lsm.c       | 2 +-
>  security/commoncap.c          | 2 +-
>  security/security.c           | 2 +-
>  security/selinux/hooks.c      | 2 +-
>  7 files changed, 10 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 6bb55e61e8e8..fd3844e11077 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -36,7 +36,7 @@ LSM_HOOK(int, 0, binder_transfer_file, const struct cred *from,
>  LSM_HOOK(int, 0, ptrace_access_check, struct task_struct *child,
>          unsigned int mode)
>  LSM_HOOK(int, 0, ptrace_traceme, struct task_struct *parent)
> -LSM_HOOK(int, 0, capget, struct task_struct *target, kernel_cap_t *effective,
> +LSM_HOOK(int, 0, capget, const struct task_struct *target, kernel_cap_t *effective,
>          kernel_cap_t *inheritable, kernel_cap_t *permitted)
>  LSM_HOOK(int, 0, capset, struct cred *new, const struct cred *old,
>          const kernel_cap_t *effective, const kernel_cap_t *inheritable,
> diff --git a/include/linux/security.h b/include/linux/security.h
> index e2734e9e44d5..fef65d0e522d 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -145,7 +145,8 @@ extern int cap_capable(const struct cred *cred, struct user_namespace *ns,
>  extern int cap_settime(const struct timespec64 *ts, const struct timezone *tz);
>  extern int cap_ptrace_access_check(struct task_struct *child, unsigned int mode);
>  extern int cap_ptrace_traceme(struct task_struct *parent);
> -extern int cap_capget(struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted);
> +extern int cap_capget(const struct task_struct *target, kernel_cap_t *effective,
> +                                         kernel_cap_t *inheritable, kernel_cap_t *permitted);

Don't resubmit the patch just for this, I'll fix it during the merge,
but generally nice to make sure the wrapped lines are aligned with the
previous line; look at the security_cap_get() declaration (below) in
this patch to see an example.

>  extern int cap_capset(struct cred *new, const struct cred *old,
>                       const kernel_cap_t *effective,
>                       const kernel_cap_t *inheritable,
> @@ -271,7 +272,7 @@ int security_binder_transfer_file(const struct cred *from,
>                                   const struct cred *to, struct file *file);
>  int security_ptrace_access_check(struct task_struct *child, unsigned int mode);
>  int security_ptrace_traceme(struct task_struct *parent);
> -int security_capget(struct task_struct *target,
> +int security_capget(const struct task_struct *target,
>                     kernel_cap_t *effective,
>                     kernel_cap_t *inheritable,
>                     kernel_cap_t *permitted);
> @@ -553,7 +554,7 @@ static inline int security_ptrace_traceme(struct task_struct *parent)
>         return cap_ptrace_traceme(parent);
>  }
>
> -static inline int security_capget(struct task_struct *target,
> +static inline int security_capget(const struct task_struct *target,
>                                    kernel_cap_t *effective,
>                                    kernel_cap_t *inheritable,
>                                    kernel_cap_t *permitted)
> diff --git a/kernel/capability.c b/kernel/capability.c
> index 3e058f41df32..67bdee3414dd 100644
> --- a/kernel/capability.c
> +++ b/kernel/capability.c
> @@ -112,7 +112,7 @@ static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
>         int ret;
>
>         if (pid && (pid != task_pid_vnr(current))) {
> -               struct task_struct *target;
> +               const struct task_struct *target;
>
>                 rcu_read_lock();
>
> diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
> index f431251ffb91..12dd96c3b2f0 100644
> --- a/security/apparmor/lsm.c
> +++ b/security/apparmor/lsm.c
> @@ -144,7 +144,7 @@ static int apparmor_ptrace_traceme(struct task_struct *parent)
>  }
>
>  /* Derived from security/commoncap.c:cap_capget */
> -static int apparmor_capget(struct task_struct *target, kernel_cap_t *effective,
> +static int apparmor_capget(const struct task_struct *target, kernel_cap_t *effective,
>                            kernel_cap_t *inheritable, kernel_cap_t *permitted)
>  {
>         struct aa_label *label;
> diff --git a/security/commoncap.c b/security/commoncap.c
> index 0b3fc2f3afe7..5fd64d3e5bfd 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -197,7 +197,7 @@ int cap_ptrace_traceme(struct task_struct *parent)
>   * This function retrieves the capabilities of the nominated task and returns
>   * them to the caller.
>   */
> -int cap_capget(struct task_struct *target, kernel_cap_t *effective,
> +int cap_capget(const struct task_struct *target, kernel_cap_t *effective,
>                kernel_cap_t *inheritable, kernel_cap_t *permitted)
>  {
>         const struct cred *cred;
> diff --git a/security/security.c b/security/security.c
> index d5ff7ff45b77..fb2d93b481f1 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -893,7 +893,7 @@ int security_ptrace_traceme(struct task_struct *parent)
>   *
>   * Return: Returns 0 if the capability sets were successfully obtained.
>   */
> -int security_capget(struct task_struct *target,
> +int security_capget(const struct task_struct *target,
>                     kernel_cap_t *effective,
>                     kernel_cap_t *inheritable,
>                     kernel_cap_t *permitted)
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 79b4890e9936..ff42d49f1b41 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -2056,7 +2056,7 @@ static int selinux_ptrace_traceme(struct task_struct *parent)
>                             SECCLASS_PROCESS, PROCESS__PTRACE, NULL);
>  }
>
> -static int selinux_capget(struct task_struct *target, kernel_cap_t *effective,
> +static int selinux_capget(const struct task_struct *target, kernel_cap_t *effective,
>                           kernel_cap_t *inheritable, kernel_cap_t *permitted)
>  {
>         return avc_has_perm(current_sid(), task_sid_obj(target),
> --
> 2.34.1

-- 
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