This is a note to let you know that I've just added the patch titled block: Check ADMIN before NICE for IOPRIO_CLASS_RT to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: block-check-admin-before-nice-for-ioprio_class_rt.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 94c4b4fd25e6c3763941bdec3ad54f2204afa992 Mon Sep 17 00:00:00 2001 From: Alistair Delva <adelva@xxxxxxxxxx> Date: Mon, 15 Nov 2021 18:16:55 +0000 Subject: block: Check ADMIN before NICE for IOPRIO_CLASS_RT From: Alistair Delva <adelva@xxxxxxxxxx> commit 94c4b4fd25e6c3763941bdec3ad54f2204afa992 upstream. 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 <adelva@xxxxxxxxxx> Cc: Khazhismel Kumykov <khazhy@xxxxxxxxxx> Cc: Bart Van Assche <bvanassche@xxxxxxx> Cc: Serge Hallyn <serge@xxxxxxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Paul Moore <paul@xxxxxxxxxxxxxx> Cc: selinux@xxxxxxxxxxxxxxx Cc: linux-security-module@xxxxxxxxxxxxxxx Cc: kernel-team@xxxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx # v5.14+ Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx> Acked-by: Serge Hallyn <serge@xxxxxxxxxx> Link: https://lore.kernel.org/r/20211115181655.3608659-1-adelva@xxxxxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- block/ioprio.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- 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 */ Patches currently in stable-queue which might be from adelva@xxxxxxxxxx are queue-5.15/block-check-admin-before-nice-for-ioprio_class_rt.patch