[PATCH 2/3] lsm: introduce security_lsm_manage_policy hook

[Tetsuo Handa]

On 2025/05/06 23:32, Maxime Bélair wrote:
> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> index dcaad8818679..b39e6635a7d5 100644
> --- a/security/lsm_syscalls.c
> +++ b/security/lsm_syscalls.c
> @@ -122,5 +122,10 @@ SYSCALL_DEFINE3(lsm_list_modules, u64 __user *, ids, u32 __user *, size,
>  SYSCALL_DEFINE5(lsm_manage_policy, u32, lsm_id, u32, op, void __user *, buf, u32
>  		__user *, size, u32, flags)
>  {
> -	return 0;
> +	size_t usize;
> +
> +	if (get_user(usize, size))
> +		return -EFAULT;
> +
> +	return security_lsm_manage_policy(lsm_id, op, buf, usize, flags);
>  }

syzbot will report user-controlled unbounded huge size memory allocation attempt. ;-)

This interface might be fine for AppArmor, but TOMOYO won't use this interface because
TOMOYO's policy is line-oriented ASCII text data where the destination is switched via
pseudo‑filesystem's filename; use of filename helps restricting which type of policy
can be manipulated by which process.