From: Alistair Delva adelva@google.com
stable inclusion form stable-v5.10.82 commit cc73242889b5d24a7449bb1f8ca46d2768c3496f bugzilla: 185877 https://gitee.com/openeuler/kernel/issues/I4QU6V
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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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@google.com Cc: Khazhismel Kumykov khazhy@google.com Cc: Bart Van Assche bvanassche@acm.org Cc: Serge Hallyn serge@hallyn.com Cc: Jens Axboe axboe@kernel.dk Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Paul Moore paul@paul-moore.com 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 bvanassche@acm.org Acked-by: Serge Hallyn serge@hallyn.com Link: https://lore.kernel.org/r/20211115181655.3608659-1-adelva@google.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Chen Jun chenjun102@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- block/ioprio.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/block/ioprio.c b/block/ioprio.c index 364d2294ba90..84da6c71b2cc 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 */