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 085758615A; Tue, 17 Dec 2024 17:22:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734456155; cv=none; b=Q6AF0v0vkSKpzafsVc9YYsq9Pap5iPYAbOHaFQXRBdPWxuw6ze1xqQ48iP6YctNSFwRMV2BB0Bs/gHW7sAqkXsNmBaBsQLYHjf55t02UcwbY0Ig3k4oG6d2bOZdSjjs5kg36eqzOwhCKPzfS1CLKJm40S5GDRxIZyOCFeaDqPkE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734456155; c=relaxed/simple; bh=SoIzgga6POdT4kqmPjWGRxLDbra8w+MNVw+EDF0XGzQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=I6WaeAb0mypptx/elOxBLHk8VJ1N2Q67SJrGyiaRkDLgo0pSRBUuS4tSV9G7w+z25GoDO5H1Autz+6UCpaQQD1ERn5CxtPGlN20nKU8oLLkntKNRLFU1eWflwZn9lAW4TokoLQ0sLHg+tOTyR4ZlxRMeokyCfzGbLCDYxacpepE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=f1xMf43A; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="f1xMf43A" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8227FC4CED3; Tue, 17 Dec 2024 17:22:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1734456154; bh=SoIzgga6POdT4kqmPjWGRxLDbra8w+MNVw+EDF0XGzQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=f1xMf43ATcM6mkDTIhw2TMXJr6Cu7xvsilJHRtjOvPvgfqJ1BIImD9moFa3OXtFkg UUxgTVMcGRovR38gP90lCryFc0sUlOlVtz2giitUMxFus6KoWXhZhFzljUMHud6xTA m4mn5NE1WBrnYZIzMvvTBwJkj71NuoN5ZUCi+11o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Phil Sutter , Pablo Neira Ayuso , Sasha Levin Subject: [PATCH 6.6 079/109] netfilter: IDLETIMER: Fix for possible ABBA deadlock Date: Tue, 17 Dec 2024 18:08:03 +0100 Message-ID: <20241217170536.682639359@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241217170533.329523616@linuxfoundation.org> References: <20241217170533.329523616@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Phil Sutter [ Upstream commit f36b01994d68ffc253c8296e2228dfe6e6431c03 ] Deletion of the last rule referencing a given idletimer may happen at the same time as a read of its file in sysfs: | ====================================================== | WARNING: possible circular locking dependency detected | 6.12.0-rc7-01692-g5e9a28f41134-dirty #594 Not tainted | ------------------------------------------------------ | iptables/3303 is trying to acquire lock: | ffff8881057e04b8 (kn->active#48){++++}-{0:0}, at: __kernfs_remove+0x20 | | but task is already holding lock: | ffffffffa0249068 (list_mutex){+.+.}-{3:3}, at: idletimer_tg_destroy_v] | | which lock already depends on the new lock. A simple reproducer is: | #!/bin/bash | | while true; do | iptables -A INPUT -i foo -j IDLETIMER --timeout 10 --label "testme" | iptables -D INPUT -i foo -j IDLETIMER --timeout 10 --label "testme" | done & | while true; do | cat /sys/class/xt_idletimer/timers/testme >/dev/null | done Avoid this by freeing list_mutex right after deleting the element from the list, then continuing with the teardown. Fixes: 0902b469bd25 ("netfilter: xtables: idletimer target implementation") Signed-off-by: Phil Sutter Signed-off-by: Pablo Neira Ayuso Signed-off-by: Sasha Levin --- net/netfilter/xt_IDLETIMER.c | 52 +++++++++++++++++++----------------- 1 file changed, 28 insertions(+), 24 deletions(-) diff --git a/net/netfilter/xt_IDLETIMER.c b/net/netfilter/xt_IDLETIMER.c index f8b25b6f5da7..9869ef3c2ab3 100644 --- a/net/netfilter/xt_IDLETIMER.c +++ b/net/netfilter/xt_IDLETIMER.c @@ -409,21 +409,23 @@ static void idletimer_tg_destroy(const struct xt_tgdtor_param *par) mutex_lock(&list_mutex); - if (--info->timer->refcnt == 0) { - pr_debug("deleting timer %s\n", info->label); - - list_del(&info->timer->entry); - timer_shutdown_sync(&info->timer->timer); - cancel_work_sync(&info->timer->work); - sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr); - kfree(info->timer->attr.attr.name); - kfree(info->timer); - } else { + if (--info->timer->refcnt > 0) { pr_debug("decreased refcnt of timer %s to %u\n", info->label, info->timer->refcnt); + mutex_unlock(&list_mutex); + return; } + pr_debug("deleting timer %s\n", info->label); + + list_del(&info->timer->entry); mutex_unlock(&list_mutex); + + timer_shutdown_sync(&info->timer->timer); + cancel_work_sync(&info->timer->work); + sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr); + kfree(info->timer->attr.attr.name); + kfree(info->timer); } static void idletimer_tg_destroy_v1(const struct xt_tgdtor_param *par) @@ -434,25 +436,27 @@ static void idletimer_tg_destroy_v1(const struct xt_tgdtor_param *par) mutex_lock(&list_mutex); - if (--info->timer->refcnt == 0) { - pr_debug("deleting timer %s\n", info->label); - - list_del(&info->timer->entry); - if (info->timer->timer_type & XT_IDLETIMER_ALARM) { - alarm_cancel(&info->timer->alarm); - } else { - timer_shutdown_sync(&info->timer->timer); - } - cancel_work_sync(&info->timer->work); - sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr); - kfree(info->timer->attr.attr.name); - kfree(info->timer); - } else { + if (--info->timer->refcnt > 0) { pr_debug("decreased refcnt of timer %s to %u\n", info->label, info->timer->refcnt); + mutex_unlock(&list_mutex); + return; } + pr_debug("deleting timer %s\n", info->label); + + list_del(&info->timer->entry); mutex_unlock(&list_mutex); + + if (info->timer->timer_type & XT_IDLETIMER_ALARM) { + alarm_cancel(&info->timer->alarm); + } else { + timer_shutdown_sync(&info->timer->timer); + } + cancel_work_sync(&info->timer->work); + sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr); + kfree(info->timer->attr.attr.name); + kfree(info->timer); } -- 2.39.5