Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9DB1C05027 for ; Tue, 14 Feb 2023 21:28:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232094AbjBNV2w (ORCPT ); Tue, 14 Feb 2023 16:28:52 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51850 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232890AbjBNV2t (ORCPT ); Tue, 14 Feb 2023 16:28:49 -0500 Received: from smtp-fw-80007.amazon.com (smtp-fw-80007.amazon.com [99.78.197.218]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0F072170F; Tue, 14 Feb 2023 13:28:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1676410100; x=1707946100; h=from:to:cc:subject:date:message-id:mime-version: content-transfer-encoding; bh=4I2V3gdJkdElaJmerC9fANC2cqgGxvR49nBswatWMb4=; b=CzvcUrgV3ZnJQzD+us4O+hw4akS5Lxd7w91SF/1wo9+AVwgJzSVq3G8A cZY29EdQPxeduCN4Pstu3PrT4MLf1Y18FIMr/IKHpMBVT6oK1ppCQup2L +53B6pFlcnirlNi+omkVyhr3i6CMwBXU5jB9BPCHaeYyQsis3doT3uwOn c=; X-IronPort-AV: E=Sophos;i="5.97,297,1669075200"; d="scan'208";a="181892903" Received: from pdx4-co-svc-p1-lb2-vlan3.amazon.com (HELO email-inbound-relay-pdx-2b-m6i4x-cadc3fbd.us-west-2.amazon.com) ([10.25.36.214]) by smtp-border-fw-80007.pdx80.corp.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Feb 2023 21:27:32 +0000 Received: from EX13MTAUWB002.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan2.pdx.amazon.com [10.236.137.194]) by email-inbound-relay-pdx-2b-m6i4x-cadc3fbd.us-west-2.amazon.com (Postfix) with ESMTPS id BF4F9A0F1A; Tue, 14 Feb 2023 21:27:31 +0000 (UTC) Received: from EX19D010UWA004.ant.amazon.com (10.13.138.204) by EX13MTAUWB002.ant.amazon.com (10.43.161.202) with Microsoft SMTP Server (TLS) id 15.0.1497.45; Tue, 14 Feb 2023 21:27:31 +0000 Received: from u9aa42af9e4c55a.ant.amazon.com (10.187.170.8) by EX19D010UWA004.ant.amazon.com (10.13.138.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.24; Tue, 14 Feb 2023 21:27:30 +0000 From: Munehisa Kamata To: CC: , , , , , , , , Subject: [PATCH v4] sched/psi: fix use-after-free in ep_remove_wait_queue() Date: Tue, 14 Feb 2023 13:27:05 -0800 Message-ID: <20230214212705.4058045-1-kamatam@amazon.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.187.170.8] X-ClientProxiedBy: EX19D040UWA001.ant.amazon.com (10.13.139.22) To EX19D010UWA004.ant.amazon.com (10.13.138.204) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If a non-root cgroup gets removed when there is a thread that registered trigger and is polling on a pressure file within the cgroup, the polling waitqueue gets freed in the following path. do_rmdir cgroup_rmdir kernfs_drain_open_files cgroup_file_release cgroup_pressure_release psi_trigger_destroy However, the polling thread still has a reference to the pressure file and will access the freed waitqueue when the file is closed or upon exit. fput ep_eventpoll_release ep_free ep_remove_wait_queue remove_wait_queue This results in use-after-free as pasted below. The fundamental problem here is that cgroup_file_release() (and consequently waitqueue's lifetime) is not tied to the file's real lifetime. Using wake_up_pollfree() here might be less than ideal, but it is in line with the comment at commit 42288cb44c4b ("wait: add wake_up_pollfree()") since the waitqueue's lifetime is not tied to file's one and can be considered as another special case. While this would be fixable by somehow making cgroup_file_release() be tied to the fput(), it would require sizable refactoring at cgroups or higher layer which might be more justifiable if we identify more cases like this. BUG: KASAN: use-after-free in _raw_spin_lock_irqsave+0x60/0xc0 Write of size 4 at addr ffff88810e625328 by task a.out/4404 CPU: 19 PID: 4404 Comm: a.out Not tainted 6.2.0-rc6 #38 Hardware name: Amazon EC2 c5a.8xlarge/, BIOS 1.0 10/16/2017 Call Trace: dump_stack_lvl+0x73/0xa0 print_report+0x16c/0x4e0 ? _printk+0x59/0x80 ? __virt_addr_valid+0xb8/0x130 ? _raw_spin_lock_irqsave+0x60/0xc0 kasan_report+0xc3/0xf0 ? _raw_spin_lock_irqsave+0x60/0xc0 kasan_check_range+0x2d2/0x310 _raw_spin_lock_irqsave+0x60/0xc0 remove_wait_queue+0x1a/0xa0 ep_free+0x12c/0x170 ep_eventpoll_release+0x26/0x30 __fput+0x202/0x400 task_work_run+0x11d/0x170 do_exit+0x495/0x1130 ? update_cfs_rq_load_avg+0x2c2/0x2e0 do_group_exit+0x100/0x100 get_signal+0xd67/0xde0 ? finish_task_switch+0x15f/0x3a0 arch_do_signal_or_restart+0x2a/0x2b0 exit_to_user_mode_prepare+0x94/0x100 syscall_exit_to_user_mode+0x20/0x40 do_syscall_64+0x52/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd RIP: 0033:0x7f8e392bfb91 Code: Unable to access opcode bytes at 0x7f8e392bfb67. RSP: 002b:00007fff261e08d8 EFLAGS: 00000246 ORIG_RAX: 0000000000000022 RAX: fffffffffffffdfe RBX: 0000000000000000 RCX: 00007f8e392bfb91 RDX: 0000000000000001 RSI: 00007fff261e08e8 RDI: 0000000000000004 RBP: 00007fff261e0920 R08: 0000000000400780 R09: 00007f8e3960f240 R10: 00000000000003df R11: 0000000000000246 R12: 00000000004005a0 R13: 00007fff261e0a00 R14: 0000000000000000 R15: 0000000000000000 Allocated by task 4404: kasan_set_track+0x3d/0x60 __kasan_kmalloc+0x85/0x90 psi_trigger_create+0x113/0x3e0 pressure_write+0x146/0x2e0 cgroup_file_write+0x11c/0x250 kernfs_fop_write_iter+0x186/0x220 vfs_write+0x3d8/0x5c0 ksys_write+0x90/0x110 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd Freed by task 4407: kasan_set_track+0x3d/0x60 kasan_save_free_info+0x27/0x40 ____kasan_slab_free+0x11d/0x170 slab_free_freelist_hook+0x87/0x150 __kmem_cache_free+0xcb/0x180 psi_trigger_destroy+0x2e8/0x310 cgroup_file_release+0x4f/0xb0 kernfs_drain_open_files+0x165/0x1f0 kernfs_drain+0x162/0x1a0 __kernfs_remove+0x1fb/0x310 kernfs_remove_by_name_ns+0x95/0xe0 cgroup_addrm_files+0x67f/0x700 cgroup_destroy_locked+0x283/0x3c0 cgroup_rmdir+0x29/0x100 kernfs_iop_rmdir+0xd1/0x140 vfs_rmdir+0xfe/0x240 do_rmdir+0x13d/0x280 __x64_sys_rmdir+0x2c/0x30 do_syscall_64+0x43/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd v4: updated commit message v3: updated commit message and the comment in the code v2: updated commit message Link: https://lore.kernel.org/lkml/20230106224859.4123476-1-kamatam@amazon.com/ Fixes: 0e94682b73bf ("psi: introduce psi monitor") Cc: stable@vger.kernel.org Signed-off-by: Munehisa Kamata Signed-off-by: Mengchi Cheng Acked-by: Suren Baghdasaryan --- kernel/sched/psi.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c index 8ac8b81bfee6..02e011cabe91 100644 --- a/kernel/sched/psi.c +++ b/kernel/sched/psi.c @@ -1343,10 +1343,11 @@ void psi_trigger_destroy(struct psi_trigger *t) group = t->group; /* - * Wakeup waiters to stop polling. Can happen if cgroup is deleted - * from under a polling process. + * Wakeup waiters to stop polling and clear the queue to prevent it from + * being accessed later. Can happen if cgroup is deleted from under a + * polling process. */ - wake_up_interruptible(&t->event_wait); + wake_up_pollfree(&t->event_wait); mutex_lock(&group->trigger_lock); -- 2.38.1