Android InstantApp cannot create Realm instance

[pmpuro]

The constructor of Realm fails with the following exception:

2021-10-12 13:12:07.981 676-676/? E/audit: type=1400 audit(1634033527.971:7153): avc:  denied  { create } for  pid=6348 comm="com.example.app" name="access_control.new_commit.cv" scontext=u:r:ephemeral_app:s0:c126,c257,c512,c768 tcontext=u:object_r:app_data_file:s0:c126,c257,c512,c768 tclass=fifo_file permissive=0 SEPF_SM-A805F_11_0010 audit_filtered
2021-10-12 13:12:07.981 676-676/? E/audit: type=1300 audit(1634033527.971:7153): arch=c00000b7 syscall=33 success=no exit=-13 a0=ffffff9c a1=b400006f85c120d0 a2=1180 a3=0 items=0 ppid=696 pid=6348 auid=4294967295 uid=10382 gid=10382 euid=10382 suid=10382 fsuid=10382 egid=10382 sgid=10382 fsgid=10382 tty=(none) ses=4294967295 comm="com.example.app" exe="/system/bin/app_process64" subj=u:r:ephemeral_app:s0:c126,c257,c512,c768 key=(null)
2021-10-12 13:12:07.981 676-676/? E/audit: type=1327 audit(1634033527.971:7153): proctitle="com.example.app"
2021-10-12 13:12:07.984 6348-6348/? E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.app, PID: 6348
    java.lang.RuntimeException: Unable to create application com.example.app.app.Application: java.lang.RuntimeException: [2]: Read-only file system
        at android.app.ActivityThread.handleMakeApplication(ActivityThread.java:7512)
        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:7446)
        at android.app.ActivityThread.access$1400(ActivityThread.java:301)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2148)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:246)
        at android.app.ActivityThread.main(ActivityThread.java:8512)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1139)
     Caused by: java.lang.RuntimeException: [2]: Read-only file system
        at io.realm.interop.realmcJNI.realm_open(Native Method)
        at io.realm.interop.realmc.realm_open(realmc.java:291)
        at io.realm.interop.RealmInterop.realm_open(RealmInterop.kt:139)
        at io.realm.interop.RealmInterop.realm_open$default(RealmInterop.kt:138)
        at io.realm.Realm.<init>(Realm.kt:117)
        at com.example.app.shared.impl.db.Db.<init>(Db.kt:27)

The name nor path are not specified in the RealmConfiguration that is given to the constructor.

It seems that the actual data base file and a lock files are created. However, the run-time exception is thrown saying "Read-only file system". As I understand the first line of the log, access_control.new_commit.cv FIFO file is tried to be created but denied by the sandbox of InstantApp.

[pmpuro]

I used the 0.5.0 version.

[rorbech]

Is this 100% reproducible? Also on different devices?

[pmpuro]

Yes, that's reproducible 100 %. I've tried with two devices: Samsung A80 (A805F)/Android 11 and Nokia 7.2.

I'll attach a link to a repo shortly.

[pmpuro]

An example code can be found in this repo.

See that you need to run it as an InstantApp to see the error. Launching it as a regular app works.

Also, note that the original stack trace is from our private KMM project, but the problem can be seen in a Kotlin Android app project as well.

[nhachicha]

Hi @pmpuro thanks for the repro, I can reproduce the error, it's unfortunately related to SELinux default policy on Android preventing the creation of the named pipes as you can see in the log

avc: denied { create } for name="access_control.new_commit.cv" scontext=u:r:ephemeral_app:s0:c156,c256,c512,c768 tcontext=u:object_r:app_data_file:s0:c156,c256,c512,c768 tclass=fifo_file permissive=0

The rest of Realm files are created correctly in the internal storage though (when running in Instant App mode).
I don't understand why Google set a default policy that prevents creating pipes inside an already writable folder (maybe a feature request/ticket could be created in their issue tracker)

Could you delay the usage of Realm until the app is installed? you can detect it by InstantApps.getPackageManagerCompat(this).isInstantApp

[pmpuro]

Thanks for response. Okay, I realized that it's about Android itself. That's a shame still.

[pmpuro]

Filed an issue on this for Google.