[Magisk] manos78:
Regarding this problem...

http://xdaforums.com/showpost.php?p=73698122&postcount=3266

I see that the trouble is the call to "xmount()" at "mount_image()@img.c"

(http://github.com/topjohnwu/Magisk/...8364186159990274849c8035/jni/utils/img.c#L134)

This call seems that is running without sufficient privileges. When the full Android is running, in the shell after a "su" I can execute the full command "mount /dev/block/loop1 /dev/source" and it works!

So the problems seems to be that the process "post_fs_data" (post_fs_data()@bootstages.c) doesn't have sufficient privileges for execute the mount of the loop device.

Here the result of "ls -lZ /dev/block/" in my device:

1|potter_n:/dev # ls -lZ /dev/block/
total 0
lrwxrwxrwx 1 root root u:object_r:block_device:s0 33 1970-01-04 12:47 bootdevice -> /dev/block/platform/7824900.sdhci
brw------- 1 root root u:object_r:loop_device:s0 7, 0 1970-01-04 12:47 loop0
brw------- 1 root root u:object_r:loop_device:s0 7, 1 1970-01-04 12:47 loop1
brw------- 1 root root u:object_r:loop_device:s0 7, 2 1970-01-04 12:47 loop2
brw------- 1 root root u:object_r:loop_device:s0 7, 3 1970-01-04 12:47 loop3
brw------- 1 root root u:object_r:loop_device:s0 7, 4 1970-01-04 12:47 loop4
brw------- 1 root root u:object_r:loop_device:s0 7, 5 1970-01-04 12:47 loop5
brw------- 1 root root u:object_r:loop_device:s0 7, 6 1970-01-04 12:47 loop6
brw------- 1 root root u:object_r:loop_device:s0 7, 7 1970-01-04 12:47 loop7
brw------- 1 root root u:object_r:root_block_device:s0 179, 0 1970-01-04 12:47 mmcblk0
brw------- 1 root root u:object_r:block_device:s0 179, 1 1970-01-04 12:47 mmcblk0p1
brw------- 1 root root u:object_r:block_device:s0 179, 10 1970-01-04 12:47 mmcblk0p10
brw------- 1 root root u:object_r:block_device:s0 179, 11 1970-01-04 12:47 mmcblk0p11
brw------- 1 root root u:object_r:block_device:s0 179, 12 1970-01-04 12:47 mmcblk0p12
brw------- 1 root root u:object_r:block_device:s0 179, 13 1970-01-04 12:47 mmcblk0p13
brw------- 1 root root u:object_r:block_device:s0 179, 14 1970-01-04 12:47 mmcblk0p14
brw------- 1 root root u:object_r:block_device:s0 179, 15 1970-01-04 12:47 mmcblk0p15
brw------- 1 root root u:object_r:block_device:s0 179, 16 1970-01-04 12:47 mmcblk0p16
brw------- 1 root root u:object_r:block_device:s0 179, 17 1970-01-04 12:47 mmcblk0p17
brw------- 1 root root u:object_r:block_device:s0 179, 18 1970-01-04 12:47 mmcblk0p18
brw------- 1 root root u:object_r:firmware_block_device:s0 179, 19 1970-01-04 12:47 mmcblk0p19
brw------- 1 root root u:object_r:rpmb_device:s0 179, 2 1970-01-04 12:47 mmcblk0p2
brw------- 1 root root u:object_r:modem_efs_partition_device:s0 179, 20 1970-01-04 12:47 mmcblk0p20
brw------- 1 root root u:object_r:ssd_device:s0 179, 21 1970-01-04 12:47 mmcblk0p21
brw------- 1 root root u:object_r:dsp_block_device:s0 179, 22 1970-01-04 12:47 mmcblk0p22
brw------- 1 root root u:object_r:block_device:s0 179, 23 1970-01-04 12:47 mmcblk0p23
brw------- 1 root root u:object_r:block_device:s0 179, 24 1970-01-04 12:47 mmcblk0p24
brw-rw---- 1 mot_tcmd system u:object_r:utags_block_device:s0 179, 25 2017-09-07 09:55 mmcblk0p25
brw-rw---- 1 mot_tcmd system u:object_r:utags_block_device:s0 179, 26 2017-09-07 09:55 mmcblk0p26
brw------- 1 root root u:object_r:modem_efs_partition_device:s0 179, 27 1970-01-04 12:47 mmcblk0p27
brw------- 1 root root u:object_r:modem_efs_partition_device:s0 179, 28 2017-09-07 09:57 mmcblk0p28
brw------- 1 root root u:object_r:modem_efs_partition_device:s0 179, 29 1970-01-04 12:47 mmcblk0p29
brw------- 1 root root u:object_r:block_device:s0 179, 3 1970-01-04 12:47 mmcblk0p3
brw------- 1 root root u:object_r:persist_block_device:s0 179, 30 1970-01-04 12:47 mmcblk0p30
brw------- 1 system system u:object_r:frp_block_device:s0 179, 31 2017-09-07 09:55 mmcblk0p31
brw-rw---- 1 root mot_tcmd u:object_r:cid_block_device:s0 259, 0 1970-01-04 12:47 mmcblk0p32
brw------- 1 root root u:object_r:block_device:s0 259, 1 1970-01-04 12:47 mmcblk0p33
brw------- 1 root root u:object_r:block_device:s0 259, 2 1970-01-04 12:47 mmcblk0p34
brw------- 1 root root u:object_r:metadata_block_device:s0 259, 3 1970-01-04 12:47 mmcblk0p35
brw------- 1 root root u:object_r:kpan_block_device:s0 259, 4 1970-01-04 12:47 mmcblk0p36
brw------- 1 root root u:object_r:boot_block_device:s0 259, 5 1970-01-04 12:47 mmcblk0p37
brw------- 1 root root u:object_r:recovery_block_device:s0 259, 6 1970-01-04 12:47 mmcblk0p38
brw------- 1 root root u:object_r:misc_block_device:s0 259, 7 2017-09-07 09:56 mmcblk0p39
brw------- 1 root root u:object_r:block_device:s0 179, 4 1970-01-04 12:47 mmcblk0p4
brw------- 1 root root u:object_r:block_device:s0 259, 8 1970-01-04 12:47 mmcblk0p40
brw------- 1 root root u:object_r:block_device:s0 259, 9 1970-01-04 12:47 mmcblk0p41
brw------- 1 root root u:object_r:dip_device:s0 259, 10 1970-01-04 12:47 mmcblk0p42
brw------- 1 root root u:object_r:block_device:s0 259, 11 1970-01-04 12:47 mmcblk0p43
brw-r----- 1 root log u:object_r:bllogs_block_device:s0 259, 12 1970-01-04 12:47 mmcblk0p44
brw------- 1 root root u:object_r:block_device:s0 259, 13 1970-01-04 12:47 mmcblk0p45
brw------- 1 root root u:object_r:mba_debug_dev:s0 259, 14 1970-01-04 12:47 mmcblk0p46
brw------- 1 root root u:object_r:block_device:s0 259, 15 1970-01-04 12:47 mmcblk0p47
brw------- 1 root root u:object_r:block_device:s0 259, 16 1970-01-04 12:47 mmcblk0p48
brw------- 1 root root u:object_r:block_device:s0 259, 17 1970-01-04 12:47 mmcblk0p49
brw------- 1 root root u:object_r:block_device:s0 179, 5 1970-01-04 12:47 mmcblk0p5
brw------- 1 root root u:object_r:hw_block_device:s0 259, 18 1970-01-04 12:47 mmcblk0p50
brw------- 1 root root u:object_r:oemfs_block_device:s0 259, 19 1970-01-04 12:47 mmcblk0p51
brw------- 1 root root u:object_r:cache_block_device:s0 259, 20 1970-01-04 12:47 mmcblk0p52
brw------- 1 root root u:object_r:system_block_device:s0 259, 21 1970-01-04 12:47 mmcblk0p53
brw------- 1 root root u:object_r:userdata_block_device:s0 259, 22 1970-01-04 12:47 mmcblk0p54
brw------- 1 root root u:object_r:block_device:s0 179, 6 1970-01-04 12:47 mmcblk0p6
brw------- 1 root root u:object_r:block_device:s0 179, 7 1970-01-04 12:47 mmcblk0p7
brw------- 1 root root u:object_r:block_device:s0 179, 8 1970-01-04 12:47 mmcblk0p8
brw------- 1 root root u:object_r:block_device:s0 179, 9 1970-01-04 12:47 mmcblk0p9
brw------- 1 root root u:object_r:rpmb_device:s0 179, 32 1970-01-04 12:47 mmcblk0rpmb
brw------- 1 root root u:object_r:sd_device:s0 179, 64 2017-09-07 09:55 mmcblk1
brw------- 1 root root u:object_r:sd_device:s0 179, 65 2017-09-07 09:55 mmcblk1p1
drwxr-xr-x 4 root root u:object_r:block_device:s0 80 2017-09-07 09:55 platform
brw------- 1 root root u:object_r:ram_device:s0 1, 0 1970-01-04 12:47 ram0
brw------- 1 root root u:object_r:ram_device:s0 1, 1 1970-01-04 12:47 ram1
brw------- 1 root root u:object_r:ram_device:s0 1, 10 1970-01-04 12:47 ram10
brw------- 1 root root u:object_r:ram_device:s0 1, 11 1970-01-04 12:47 ram11
brw------- 1 root root u:object_r:ram_device:s0 1, 12 1970-01-04 12:47 ram12
brw------- 1 root root u:object_r:ram_device:s0 1, 13 1970-01-04 12:47 ram13
brw------- 1 root root u:object_r:ram_device:s0 1, 14 1970-01-04 12:47 ram14
brw------- 1 root root u:object_r:ram_device:s0 1, 15 1970-01-04 12:47 ram15
brw------- 1 root root u:object_r:ram_device:s0 1, 2 1970-01-04 12:47 ram2
brw------- 1 root root u:object_r:ram_device:s0 1, 3 1970-01-04 12:47 ram3
brw------- 1 root root u:object_r:ram_device:s0 1, 4 1970-01-04 12:47 ram4
brw------- 1 root root u:object_r:ram_device:s0 1, 5 1970-01-04 12:47 ram5
brw------- 1 root root u:object_r:ram_device:s0 1, 6 1970-01-04 12:47 ram6
brw------- 1 root root u:object_r:ram_device:s0 1, 7 1970-01-04 12:47 ram7
brw------- 1 root root u:object_r:ram_device:s0 1, 8 1970-01-04 12:47 ram8
brw------- 1 root root u:object_r:ram_device:s0 1, 9 1970-01-04 12:47 ram9
drwx------ 2 root root u:object_r:block_device:s0 80 2017-09-07 09:55 vold
brw------- 1 root root u:object_r:swap_block_device:s0 254, 0 1970-01-04 12:47 zram0

I feel the process needs to obtain privileges for the "loop_device" context.

I'm right?