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After I format the loop.img (formatted as ext4) I can mount it no problem.

But when I'm trying to remount loop.img from external sdcard to /data/data/com.termux/home/ubuntu20-fs/ always throw invalid argument , I already tried using busybox too.

mount -t ext4 -o loop /dev/block/loop3 /data/data/com.termux/files/home/ubuntu20-fs/
mount: '/dev/block/loop3'->'/data/data/com.termux/files/home/ubuntu20-fs/': Invalid argument

Does anyone know what happened?

image

dmesg | grep avc

Strace of busybox mount with "-t" argument

losetup:

NAME  SIZELIMIT  OFFSET  AUTOCLEAR  RO  BACK-FILE  DIO  LOG-SEC
...
/dev/block/loop3  0  0  0  0  /mnt/media_rw/6DE8-1BC6/loop.img  0  512

blkid | grep loop:

/dev/block/loop3: UUID="0746ba9e-fc09-4a32-8b5f-49aee9096cf7" BLOCK_SIZE="4096" TYPE="ext4"
Jtnqr
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  • @beeshyams IrfanLatif anyone can confirm this behavior android 10? is this a magisk selinux bug maybe? – alecxs Dec 01 '20 at 19:03
  • I don't know if that is the correct logcat or not – Jtnqr Dec 01 '20 at 23:28
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    @alecxs everything related to mounting filesystems works as expected on Android 10 too. No abnormal behavior. If the issue is related to SELinux, setenforce 0 should fix it. Also dmesg | grep avc should show the related denial log entry. @Jtnqr run mount with strace and share log. – Irfan Latif Dec 02 '20 at 03:32
  • @Jtnqr are you typing commands from termux touchpad, or do you use script, copy & paste or other keyboard? – alecxs Dec 02 '20 at 08:06
  • @alexcs I ran termux using my phone touchscreen, no script. The output I copypaste from termux except strace I'm using the -o argument. – Jtnqr Dec 02 '20 at 08:32
  • so no invisible chars and no wrong line endings. could it be that file system is unmounted dirty? does it make a difference with -t ext4 -o ro,noexec,noload,noatime – alecxs Dec 02 '20 at 16:56
  • wdym? Is this dirty unmount umount /mnt/ubuntu20-fs? – Jtnqr Dec 03 '20 at 00:36
  • i mean by any chance the ext4 journal is dirty for unknown reason – alecxs Dec 03 '20 at 15:12

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