posix acl issue

[Fabio Coatti]

Hi All, 
I'm seeing a weird behaviour wrt posix acl.
Basically it seems that they are not working, even though ACLs are enabled for 
all the filesystems on my machine.
attrs are working just fine for the same files.
Example:
> getfacl pippo 
# file: pippo 
# owner: cova 
# group: cova 
other::r-- 

> setfacl -m other::r-- pippo 
setfacl: pippo: Malformed access ACL `other::r--': Missing or wrong entry at 
entry 1 

============

also, udev uaccess rules are not applied and systemd-udevd spits out this 
message:
(this is when inserting a yubikey)
systemd-udevd[4921]: Failed to apply ACL on /dev/hidraw4: Invalid argument

kernel ACL setup:

=====
zcat /proc/config.gz | grep ACL 
CONFIG_EXT2_FS_POSIX_ACL=y 
CONFIG_EXT3_FS_POSIX_ACL=y 
CONFIG_EXT4_FS_POSIX_ACL=y 
CONFIG_XFS_POSIX_ACL=y 
CONFIG_BTRFS_FS_POSIX_ACL=y 
CONFIG_FS_POSIX_ACL=y 
CONFIG_TMPFS_POSIX_ACL=y 
CONFIG_JFFS2_FS_POSIX_ACL=y 
CONFIG_NFS_V3_ACL=y 
CONFIG_NFSD_V2_ACL=y 
CONFIG_NFSD_V3_ACL=y 
CONFIG_NFS_ACL_SUPPORT=m 
CONFIG_CIFS_ACL=y 

========
attrs seems to be ok:
> setfattr -n user.foo -v bar pippo 

> getfattr pippo 
# file: pippo 
user.foo 
=========

I tested this behaviour wit btrfs, tmpfs and ext4(ext2); 
dmesg reports that acl mount option is recognized : 
=======
EXT4-fs (dm-6): mounted filesystem with ordered data mode. Opts: acl
=======

but mount output seems to tell something different:

==========
/dev/mapper/vg0-test on /root/tt type ext4 (rw,relatime)
==========

and proc tells something even different:

==========
cat /proc/fs/ext4/dm-6/options 
rw 
bsddf 
nogrpid 
block_validity 
dioread_lock 
nodiscard 
delalloc 
nowarn_on_error 
journal_checksum 
barrier 
auto_da_alloc 
user_xattr 
acl 
noquota 
resuid=0 
resgid=0 
errors=continue 
commit=5 
min_batch_time=0 
max_batch_time=15000 
stripe=0 
data=ordered 
inode_readahead_blks=32 
init_itable=10 
max_dir_size_kb=0 
==========

Kernel is 4.18.10, but I tried several kernels on 4.18 and 4.17 series, no 
changes.
gcc 8.2.0

I'm running a gentoo machine, with vanilla sources so no external patches.
I checked all possible kernel config options and whatnot without finding 
anything obvious. 
Likely I'm missing something obvious, but after several days diggin I got no 
clues, so I would be glad of any hint or suggestions about where to look.
(please, keep me cc'ed in any answer).

Many thanks for any help.