The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x 2bd110339288c18823dcace602b63b0d8627e520 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023061126-outthink-improvise-7307@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2bd110339288c18823dcace602b63b0d8627e520 Mon Sep 17 00:00:00 2001 From: John Sperbeck jsperbeck@google.com Date: Sun, 21 May 2023 19:29:53 +0000 Subject: [PATCH] cgroup: always put cset in cgroup_css_set_put_fork

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: ef2c41cf38a7 ("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

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 625d7483951c..245cf62ce85a 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -6486,19 +6486,18 @@ static int cgroup_css_set_fork(struct kernel_clone_args *kargs) static void cgroup_css_set_put_fork(struct kernel_clone_args *kargs) __releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex) { + struct cgroup *cgrp = kargs->cgrp; + struct css_set *cset = kargs->cset; + cgroup_threadgroup_change_end(current);

+ if (cset) { + put_css_set(cset); + kargs->cset = NULL; + } + if (kargs->flags & CLONE_INTO_CGROUP) { - struct cgroup *cgrp = kargs->cgrp; - struct css_set *cset = kargs->cset; - cgroup_unlock(); - - if (cset) { - put_css_set(cset); - kargs->cset = NULL; - } - if (cgrp) { cgroup_put(cgrp); kargs->cgrp = NULL;