What were you trying to do that didn't work?

The behavior of open() on a file in a directory with the sticky bit set has changed when opening a file owned by a different user, but having the same group ownership.

Removing the sticky bit allows the open to succeed.

RHEL 7 and RHEL 8 succeeded with sticky bit set.

Please provide the package NVR for which bug is seen:

kernel 5.14.0-364.el9 (likely most/all RHEL 9 kernels)

How reproducible:

easy

Steps to reproduce

create group and two users with same group membership:

# groupadd -g 2000 group2000
# useradd -g 2000 -u 2000 user2000
# useradd -g 2000 -u 2001 user2001

create a test directory + file, set mode & ownership:

# cd /tmp
# mkdir -m 01777 testdir
# touch testdir/testfile2000
# chmod 664 testdir/testfile2000
# chown user2000:group2000 testdir/testfile2000

su to user2001, try to write file

# su user2001
# vi testdir/testfile2000
:w 

all-in-one reproducer will be attached

Expected results

Since the group ownership matches the user's group membership, the write is expected to succeed.

Actual results

The write fails with EACCES