From: Alistair Delva Date: Mon, 15 Nov 2021 18:16:55 +0000 (+0000) Subject: block: Check ADMIN before NICE for IOPRIO_CLASS_RT X-Git-Tag: v6.6.17~8536^2~23 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=94c4b4fd25e6c3763941bdec3ad54f2204afa992;p=platform%2Fkernel%2Flinux-rpi.git block: Check ADMIN before NICE for IOPRIO_CLASS_RT Booting to Android userspace on 5.14 or newer triggers the following SELinux denial: avc: denied { sys_nice } for comm="init" capability=23 scontext=u:r:init:s0 tcontext=u:r:init:s0 tclass=capability permissive=0 Init is PID 0 running as root, so it already has CAP_SYS_ADMIN. For better compatibility with older SEPolicy, check ADMIN before NICE. Fixes: 9d3a39a5f1e4 ("block: grant IOPRIO_CLASS_RT to CAP_SYS_NICE") Signed-off-by: Alistair Delva Cc: Khazhismel Kumykov Cc: Bart Van Assche Cc: Serge Hallyn Cc: Jens Axboe Cc: Greg Kroah-Hartman Cc: Paul Moore Cc: selinux@vger.kernel.org Cc: linux-security-module@vger.kernel.org Cc: kernel-team@android.com Cc: stable@vger.kernel.org # v5.14+ Reviewed-by: Bart Van Assche Acked-by: Serge Hallyn Link: https://lore.kernel.org/r/20211115181655.3608659-1-adelva@google.com Signed-off-by: Jens Axboe --- diff --git a/block/ioprio.c b/block/ioprio.c index 0e4ff24..313c14a 100644 --- a/block/ioprio.c +++ b/block/ioprio.c @@ -69,7 +69,14 @@ int ioprio_check_cap(int ioprio) switch (class) { case IOPRIO_CLASS_RT: - if (!capable(CAP_SYS_NICE) && !capable(CAP_SYS_ADMIN)) + /* + * Originally this only checked for CAP_SYS_ADMIN, + * which was implicitly allowed for pid 0 by security + * modules such as SELinux. Make sure we check + * CAP_SYS_ADMIN first to avoid a denial/avc for + * possibly missing CAP_SYS_NICE permission. + */ + if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_NICE)) return -EPERM; fallthrough; /* rt has prio field too */