On Mon, Jul 10, 2023 at 4:25 AM Leesoo Ahn <lsahn@xxxxxxxxxx> wrote:
>
> The major part, the conditional branch in selinux_mmap_addr() is always to be
> false so long as CONFIG_LSM_MMAP_MIN_ADDR is set to zero at compile time.
>
> This usually happens in some linux distros, for instance Ubuntu, which
> the config is set to zero in release version. Therefore it could be a bit
> optimized with '#if <expr>' at compile time.
If your distro is configuring LSM_MMAP_MIN_ADDR to 0, you might want
to bug them about it, because that's not a great idea for security.
And if you intend to use SELinux there, you'll want it set higher.
Default value in the Kconfig is 65536.
>
> Signed-off-by: Leesoo Ahn <lsahn@xxxxxxxxxxxxxx>
> ---
> security/selinux/hooks.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index d06e350fedee..a049aab6524b 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -3723,11 +3723,13 @@ static int selinux_mmap_addr(unsigned long addr)
> {
> int rc = 0;
>
> +#if CONFIG_LSM_MMAP_MIN_ADDR > 0
> if (addr < CONFIG_LSM_MMAP_MIN_ADDR) {
> u32 sid = current_sid();
> rc = avc_has_perm(sid, sid, SECCLASS_MEMPROTECT,
> MEMPROTECT__MMAP_ZERO, NULL);
> }
> +#endif
>
> return rc;
> }
> --
> 2.34.1
>
