Postfix with home dirs on GPFS

[Luke Sudbery]

Hello,

With home directories on IBM Spectrum Scale and selinux enabled, postfix is unable to
deliver locally. This is using RHELS8.3.

Postfix logs:


May 27 10:23:20 host-name postfix/local[1245962]: A1219F9E:
to=<[e-mail]<mailto:[e-mail]>>,
orig_to=<username>, relay=local, delay=0.03, delays=0.01/0.01/0/0.01, dsn=5.2.0,
status=bounced (cannot update mailbox /gpfs-fs/homes/u/username/Mailbox for user username.
unable to create lock file /gpfs-fs/homes/u/username/Mailbox.lock: Permission denied)

Although the actual problem is that it can't/doesn't read ~/.forward to know where
to really send the mail.

Selinux audit logs show:


type=AVC msg=audit(1622111726.610:10854499): avc:  denied  { search } for  pid=1315267
comm="local" name="/" dev="gpfs" ino=3
scontext=system_u:system_r:postfix_local_t:s0 tcontext=system_u:object_r:unlabeled_t:s0
tclass=dir permissive=0

type=SYSCALL msg=audit(1622111726.610:10854499): arch=c000003e syscall=6 success=no
exit=-13 a0=561f9a316390 a1=7ffdc7e109c0 a2=7ffdc7e109c0 a3=0 items=0 ppid=3375
pid=1315267 auid=4294967295 uid=0 gid=0 euid=606178 suid=0 fsuid=606178 egid=100 sgid=0
fsgid=100 tty=(none) ses=4294967295 comm="local"
exe="/usr/libexec/postfix/local" subj=system_u:system_r:postfix_local_t:s0
key=(null)ARCH=x86_64 SYSCALL=lstat AUID="unset" UID="root"
GID="root" EUID="username" SUID="root"
FSUID="username" EGID="users" SGID="root"
FSGID="users"

type=AVC msg=audit(1622111726.611:10854500): avc:  denied  { search } for  pid=1315267
comm="local" name="/" dev="gpfs" ino=3
scontext=system_u:system_r:postfix_local_t:s0 tcontext=system_u:object_r:unlabeled_t:s0
tclass=dir permissive=0

type=SYSCALL msg=audit(1622111726.611:10854500): arch=c000003e syscall=4 success=no
exit=-13 a0=561f9a3165c0 a1=7ffdc7e109c0 a2=7ffdc7e109c0 a3=0 items=0 ppid=3375
pid=1315267 auid=4294967295 uid=0 gid=0 euid=606178 suid=0 fsuid=606178 egid=100 sgid=0
fsgid=100 tty=(none) ses=4294967295 comm="local"
exe="/usr/libexec/postfix/local" subj=system_u:system_r:postfix_local_t:s0
key=(null)ARCH=x86_64 SYSCALL=stat AUID="unset" UID="root"
GID="root" EUID="username" SUID="root"
FSUID="username" EGID="users" SGID="root"
FSGID="users"

type=AVC msg=audit(1622111726.611:10854501): avc:  denied  { search } for  pid=1315267
comm="local" name="/" dev="gpfs" ino=3
scontext=system_u:system_r:postfix_local_t:s0 tcontext=system_u:object_r:unlabeled_t:s0
tclass=dir permissive=0

type=SYSCALL msg=audit(1622111726.611:10854501): arch=c000003e syscall=257 success=no
exit=-13 a0=ffffff9c a1=561f9a316600 a2=c1 a3=0 items=0 ppid=3375 pid=1315267
auid=4294967295 uid=0 gid=0 euid=606178 suid=0 fsuid=606178 egid=100 sgid=0 fsgid=100
tty=(none) ses=4294967295 comm="local"
exe="/usr/libexec/postfix/local" subj=system_u:system_r:postfix_local_t:s0
key=(null)ARCH=x86_64 SYSCALL=openat AUID="unset" UID="root"
GID="root" EUID="username" SUID="root"
FSUID="username" EGID="users" SGID="root"
FSGID="users"

audit2allow shows:


[root@host-name audit]# audit2allow -w -a

type=AVC msg=audit(1622111726.610:10854499): avc:  denied  { search } for  pid=1315267
comm="local" name="/" dev="gpfs" ino=3
scontext=system_u:system_r:postfix_local_t:s0 tcontext=system_u:object_r:unlabeled_t:s0
tclass=dir permissive=0

        Was caused by:

                Missing type enforcement (TE) allow rule.



                You can use audit2allow to generate a loadable module to allow this
access.



type=AVC msg=audit(1622111726.611:10854500): avc:  denied  { search } for  pid=1315267
comm="local" name="/" dev="gpfs" ino=3
scontext=system_u:system_r:postfix_local_t:s0 tcontext=system_u:object_r:unlabeled_t:s0
tclass=dir permissive=0

        Was caused by:

                Missing type enforcement (TE) allow rule.



                You can use audit2allow to generate a loadable module to allow this
access.



type=AVC msg=audit(1622111726.611:10854501): avc:  denied  { search } for  pid=1315267
comm="local" name="/" dev="gpfs" ino=3
scontext=system_u:system_r:postfix_local_t:s0 tcontext=system_u:object_r:unlabeled_t:s0
tclass=dir permissive=0

        Was caused by:

                Missing type enforcement (TE) allow rule.



                You can use audit2allow to generate a loadable module to allow this
access.



[root@host-name audit]# audit2allow -a





#============= postfix_local_t ==============

allow postfix_local_t unlabeled_t:dir search;

[root@host-name audit]#

Creating a module using these rules fixes the problem.

I've also tested creating a user with a home directory with GPFS stopped, and using
the same path that a GPFS user would have. This worked without any selinux changes, and
implies this is a problem with home dirs on GPFS, rather than just the path itself.

Should this be reported as a selinux bug?

Many thanks,

Luke

--
Luke Sudbery
Architecture, Infrastructure and Systems
Advanced Research Computing, IT Services
Room 132, Computer Centre G5, Elms Road

Please note I don't work on Monday.