domain: allow reading /proc/sys/vm/overcommit_memory

Needed for jemalloc commit:

2f970c32b527660a33fa513a76d913c812dcf7c
Modify pages_map() to support mapping uncommitted virtual memory.

avc: denied { read } for name="overcommit_memory" dev="proc" ino=10544
scontext=u:r:wificond:s0 tcontext=u:object_r:proc:s0 tclass=file

Bug: 29773242
Change-Id: I78054c1ed576a7998c4ee1d1beca2f610c589c3a

domain.te

@@ -115,6 +115,9 @@ allow domain proc:lnk_file { getattr read };
 # /proc/cpuinfo
 allow domain proc_cpuinfo:file r_file_perms;
 
+# jemalloc needs to read /proc/sys/vm/overcommit_memory
+allow domain proc_overcommit_memory:file r_file_perms;
+
 # toybox loads libselinux which stats /sys/fs/selinux/
 allow domain selinuxfs:dir search;
 allow domain selinuxfs:file getattr;

file.te

@@ -6,8 +6,8 @@ type rootfs, fs_type;
 type proc, fs_type;
 # Security-sensitive proc nodes that should not be writable to most.
 type proc_security, fs_type;
-# Type for /proc/sys/vm/drop_caches
 type proc_drop_caches, fs_type;
+type proc_overcommit_memory, fs_type;
 # proc, sysfs, or other nodes that permit configuration of kernel usermodehelpers.
 type usermodehelper, fs_type, sysfs_type;
 type qtaguid_proc, fs_type, mlstrustedobject;

genfs_contexts

@@ -23,6 +23,7 @@ genfscon proc /sys/kernel/usermodehelper u:object_r:usermodehelper:s0
 genfscon proc /sys/net u:object_r:proc_net:s0
 genfscon proc /sys/vm/mmap_min_addr u:object_r:proc_security:s0
 genfscon proc /sys/vm/drop_caches u:object_r:proc_drop_caches:s0
+genfscon proc /sys/vm/overcommit_memory u:object_r:proc_overcommit_memory:s0
 genfscon proc /uid_cputime/show_uid_stat u:object_r:proc_uid_cputime_showstat:s0
 genfscon proc /uid_cputime/remove_uid_range u:object_r:proc_uid_cputime_removeuid:s0