[ Upstream commit 2bd1103392 ]
A successful call to cgroup_css_set_fork() will always have taken
a ref on kargs->cset (regardless of CLONE_INTO_CGROUP), so always
do a corresponding put in cgroup_css_set_put_fork().
Without this, a cset and its contained css structures will be
leaked for some fork failures. The following script reproduces
the leak for a fork failure due to exceeding pids.max in the
pids controller. A similar thing can happen if we jump to the
bad_fork_cancel_cgroup label in copy_process().
[ -z "$1" ] && echo "Usage $0 pids-root" && exit 1
PID_ROOT=$1
CGROUP=$PID_ROOT/foo
[ -e $CGROUP ] && rmdir -f $CGROUP
mkdir $CGROUP
echo 5 > $CGROUP/pids.max
echo $$ > $CGROUP/cgroup.procs
fork_bomb()
{
set -e
for i in $(seq 10); do
/bin/sleep 3600 &
done
}
(fork_bomb) &
wait
echo $$ > $PID_ROOT/cgroup.procs
kill $(cat $CGROUP/cgroup.procs)
rmdir $CGROUP
Fixes: ef2c41cf38 ("clone3: allow spawning processes into cgroups")
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: John Sperbeck <jsperbeck@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
c68b4db581