Bug 36312

Summary:	User belonging to another Group has no access when chmod 0040
Product:	File System	Reporter:	ubuntuefnet
Component:	ext4	Assignee:	Jan Kara (jack)
Status:	RESOLVED INVALID
Severity:	low	CC:	jack
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	2.6.39	Subsystem:
Regression:	Yes	Bisected commit-id:

Description ubuntuefnet 2011-05-31 00:19:18 UTC

This may not be a bug, this may be intentional - however it was considered pretty damn weird when encountered and worth a mention.

Say we have user 'bob', he is the owner of file 'accounting.txt' and 'accounting.txt' has group 'staff' attributed to the file which 'bob' is a part of. If the permissions for the file only have group perms (e.g 0060), 'bob' will not be able to access 'accounting.txt', however all other users in the 'staff' group will have access.

Replication via CLI:

touch myfile.txt && chown `whoami`:`groups | awk '{print $2}'` myfile.txt && chmod 0040 myfile.txt && cat myfile.txt

System: Debian 6.0.1
Arch: x86_64
Kernel: 2.6.39

Comment 1 Jan Kara 2011-05-31 18:43:43 UTC

Yes, this works as defined in the standard. If user is the owner, we check against owner bits. If the user is not the owner, but belongs to the owner group, we check against group bits. If user falls into neither of previous cathegories, we use 'other' bits.