From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8A24C5381 for ; Mon, 19 Jun 2023 10:43:40 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 129CAC433C0; Mon, 19 Jun 2023 10:43:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1687171420; bh=wAXS9rGRh1fGK4NpglGdrw6ioq9Vv7UfKDQ0HUWyxDw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=beeyOvvpFQOsTd5iSBf4LP06q2i6iJN+Ab4WLGoT3tCLojzlI3pXMYMm906YGJTdr eCYtShie1D6sMzg8duVKMfEAGOM4dM+2al9oo1KxgEyJoXZGwE2XnGBTA2y7t1mIV0 tw9FA53J5CGEVAFjLgBQZg7iKBhil4Z2KBGLhWKc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, John Sperbeck , Tejun Heo , Sasha Levin Subject: [PATCH 6.1 005/166] cgroup: always put cset in cgroup_css_set_put_fork Date: Mon, 19 Jun 2023 12:28:02 +0200 Message-ID: <20230619102154.908246524@linuxfoundation.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230619102154.568541872@linuxfoundation.org> References: <20230619102154.568541872@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: John Sperbeck [ Upstream commit 2bd110339288c18823dcace602b63b0d8627e520 ] 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 Signed-off-by: Tejun Heo Signed-off-by: Sasha Levin --- kernel/cgroup/cgroup.c | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 002e563ec2ac8..36c95626afecc 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -6471,19 +6471,18 @@ 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 (kargs->flags & CLONE_INTO_CGROUP) { - struct cgroup *cgrp = kargs->cgrp; - struct css_set *cset = kargs->cset; + if (cset) { + put_css_set(cset); + kargs->cset = NULL; + } + if (kargs->flags & CLONE_INTO_CGROUP) { cgroup_unlock(); - - if (cset) { - put_css_set(cset); - kargs->cset = NULL; - } - if (cgrp) { cgroup_put(cgrp); kargs->cgrp = NULL; -- 2.39.2