Big files are uploaded with broken permissions

Issue Summary

Files bigger than 2.48 MB are uploaded with wrong permissions and are not readable from /media/

Steps to Reproduce

Create two files with content size 2600000 bytes and 2700000 bytes. The second file gets its access rights mangled. Reproducible for me on two separate installations.

wagtail 1.12.2, Django==1.11, python 3.5.2+ (ubuntu 16.10)

and

1.13. with python 3.5.3 (ubuntu 17.04):

django-analytical==2.3.0
django-compressor==2.2
django-redis==4.8.0
django-sekizai==0.10.0
libsass==0.13.3
psycopg2==2.7.3.1
wagtail==1.13.1
waitress==1.1.0
requests==2.18.4

This is how the files get saved in media

with the smaller ones working as expected:

Any ideas on how to resolve this issues or where to start digging?

[BertrandBordage]

Did you try setting FILE_UPLOAD_PERMISSIONS?

[gasman]

I agree. If FILE_UPLOAD_PERMISSIONS doesn’t help and testing with a FileField shows that this is Wagtail-specific, let us know and we’ll reopen.