android_system_sepolicy/ueventd.te
Nick Kralevich 31d88a704e Allow /dev/klog access, drop mknod and __null__ access
Allow vold, healthd, slideshow, and watchdogd access to /dev/kmsg.
These processes log to the kernel dmesg ring buffer, so they need
write access to that file.

Addresses the following denials:

    avc: denied { write } for pid=134 comm="watchdogd" name="kmsg" dev="tmpfs" ino=9248 scontext=u:r:watchdogd:s0 tcontext=u:object_r:kmsg_device:s0 tclass=chr_file permissive=0
    avc: denied { write } for pid=166 comm="healthd" name="kmsg" dev="tmpfs" ino=9248 scontext=u:r:healthd:s0 tcontext=u:object_r:kmsg_device:s0 tclass=chr_file permissive=0
    avc: denied { write } for pid=180 comm="vold" name="kmsg" dev="tmpfs" ino=9248 scontext=u:r:vold:s0 tcontext=u:object_r:kmsg_device:s0 tclass=chr_file permissive=0

These denials were triggered by the change in
https://android-review.googlesource.com/151209 . Prior to that change,
any code which called klog_init would (unnecessarily) create the
device node themselves, rather than using the already existing device
node.

Drop special /dev/__null__ handling from watchdogd. As of
https://android-review.googlesource.com/148288 , watchdogd no longer
creates it's own /dev/null device, so it's unnecessary for us
to allow for it.

Drop mknod from healthd, slideshow, and watchdogd. healthd and slideshow
only needed mknod to create /dev/__kmsg__, which is now obsolete.
watchdogd only needed mknod to create /dev/__kmsg__ and /dev/__null__,
which again is now obsolete.

(cherry picked from e2651972c1)

Bug: 21242418
Change-Id: If01c8001084575e7441253f0fa8b4179ae33f534
2015-06-23 16:47:49 +00:00

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# ueventd seclabel is specified in init.rc since
# it lives in the rootfs and has no unique file type.
type ueventd, domain;
tmpfs_domain(ueventd)
# TODO: why is ueventd using __kmsg__ when it should just create
# and use /dev/kmsg instead?
type_transition ueventd device:chr_file klog_device "__kmsg__";
allow ueventd klog_device:chr_file { create open write unlink };
security_access_policy(ueventd)
allow ueventd init:process sigchld;
allow ueventd self:capability { chown mknod net_admin setgid fsetid sys_rawio dac_override fowner };
allow ueventd device:file create_file_perms;
allow ueventd device:chr_file rw_file_perms;
allow ueventd sysfs:file rw_file_perms;
allow ueventd sysfs_type:{ file lnk_file } { relabelfrom relabelto setattr getattr };
allow ueventd sysfs_type:dir { relabelfrom relabelto setattr r_dir_perms };
allow ueventd sysfs_devices_system_cpu:file rw_file_perms;
allow ueventd tmpfs:chr_file rw_file_perms;
allow ueventd dev_type:dir create_dir_perms;
allow ueventd dev_type:lnk_file { create unlink };
allow ueventd dev_type:chr_file { create setattr unlink };
allow ueventd dev_type:blk_file { create setattr unlink };
allow ueventd self:netlink_kobject_uevent_socket create_socket_perms;
allow ueventd efs_file:dir search;
allow ueventd efs_file:file r_file_perms;
# Use setfscreatecon() to label /dev directories and files.
allow ueventd self:process setfscreate;
#####
##### neverallow rules
#####
# ueventd must never set properties, otherwise deadlocks may occur.
# https://android-review.googlesource.com/#/c/133120/6/init/devices.cpp@941
# No writing to the property socket, connecting to init, or setting properties.
neverallow ueventd property_socket:sock_file write;
neverallow ueventd init:unix_stream_socket connectto;
neverallow ueventd property_type:property_service set;