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 5.10-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-5.10 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-5.10/block-check-admin-before-nice-for-ioprio_class_rt.patch
