I am trying to understand file/dir permissions in linux. A user can list the files in a directory using

cd test ls -l 

Even if the user issuing above command does not have read,write or execute permission on any of the files inside the test directory, still he can list them because he/she has read permissions on the test directory.

Then why in the following scenario user B can change permissions of a file he owns but does not have write permissions of the parent directory ?

User A , make a test directory and gives other users ability to write in it

mkdir test chmod o+w test 

User B , creates a file in test folder.

cd test touch b.txt 

User A ,removes write permission of others from the directory

chmod o-w test 

User B , can successfully change permissions, even though permissions are part of directory and this user does not have write permission on the parent directory of the file he owns

chmod g-r b.txt 

why does chmod does not fail after user can not modify the directory which has the file information - permissions etc ??