Re: [PATCH 4/6] security: Replace memcpy() with __get_task_comm()

[Paul Moore <paul@paul-moore.com>]

On Sat, Jun 1, 2024 at 10:38 PM Yafang Shao <laoar.shao@gmail.com> wrote:
>
> Quoted from Linus [0]:
>
>   selinux never wanted a lock, and never wanted any kind of *consistent*
>   result, it just wanted a *stable* result.
>
> Using __get_task_comm() to read the task comm ensures that the name is
> always NUL-terminated, regardless of the source string. This approach also
> facilitates future extensions to the task comm.
>
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> LINK: https://lore.kernel.org/all/CAHk-=wivfrF0_zvf+oj6==Sh=-npJooP8chLPEfaFV0oNYTTBA@mail.gmail.com/ [0]
> Cc: Paul Moore <paul@paul-moore.com>
> Cc: James Morris <jmorris@namei.org>
> Cc: "Serge E. Hallyn" <serge@hallyn.com>
> Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
> Cc: Ondrej Mosnacek <omosnace@redhat.com>
> ---
>  security/lsm_audit.c         | 4 ++--
>  security/selinux/selinuxfs.c | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)

Similar to the audit change, as long as you sort out the
__get_task_comm() issues such that it can operate without task_lock()
this should be fine.

Acked-by: Paul Moore <paul@paul-moore.com>

> diff --git a/security/lsm_audit.c b/security/lsm_audit.c
> index 849e832719e2..a922e4339dd5 100644
> --- a/security/lsm_audit.c
> +++ b/security/lsm_audit.c
> @@ -207,7 +207,7 @@ static void dump_common_audit_data(struct audit_buffer *ab,
>         BUILD_BUG_ON(sizeof(a->u) > sizeof(void *)*2);
>
>         audit_log_format(ab, " pid=%d comm=", task_tgid_nr(current));
> -       audit_log_untrustedstring(ab, memcpy(comm, current->comm, sizeof(comm)));
> +       audit_log_untrustedstring(ab, __get_task_comm(comm, sizeof(comm), current));
>
>         switch (a->type) {
>         case LSM_AUDIT_DATA_NONE:
> @@ -302,7 +302,7 @@ static void dump_common_audit_data(struct audit_buffer *ab,
>                                 char comm[sizeof(tsk->comm)];
>                                 audit_log_format(ab, " opid=%d ocomm=", pid);
>                                 audit_log_untrustedstring(ab,
> -                                   memcpy(comm, tsk->comm, sizeof(comm)));
> +                                   __get_task_comm(comm, sizeof(comm), tsk));
>                         }
>                 }
>                 break;
> diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
> index e172f182b65c..a8a2ec742576 100644
> --- a/security/selinux/selinuxfs.c
> +++ b/security/selinux/selinuxfs.c
> @@ -708,7 +708,7 @@ static ssize_t sel_write_checkreqprot(struct file *file, const char __user *buf,
>         if (new_value) {
>                 char comm[sizeof(current->comm)];
>
> -               memcpy(comm, current->comm, sizeof(comm));
> +               __get_task_comm(comm, sizeof(comm), current);
>                 pr_err("SELinux: %s (%d) set checkreqprot to 1. This is no longer supported.\n",
>                        comm, current->pid);
>         }
> --
> 2.39.1

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