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[2620:137:e000::1:20]) by mx.google.com with ESMTP id e6-20020a170906748600b0086f05817f39si19200522ejl.39.2023.02.13.23.10.17; Mon, 13 Feb 2023 23:10:41 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@amazon.com header.s=amazon201209 header.b=OpcxD7lH; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=amazon.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231757AbjBNHEy (ORCPT + 99 others); Tue, 14 Feb 2023 02:04:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47702 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231758AbjBNHEu (ORCPT ); Tue, 14 Feb 2023 02:04:50 -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 19C2915540; Mon, 13 Feb 2023 23:04:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1676358289; x=1707894289; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=5wmH/X+5oMB6tbZAEPbXCiBvhr91wPP7JNYYz5K8YkU=; b=OpcxD7lHiuupbIjxlMfd8Ixw/8kCigVXvtdTd2XUnfpuk8MWY7BrslZv mWMDUnGA3z8l1iU8iAiLg36/Drfa/T58+AUgyH6Vrjk2HZG4Yt1AMmcrM LKKDDFMlmRcExlIwarACKi5FtNn2cmCrKYstDL3IsY5f3mH+5cwUg335x k=; X-IronPort-AV: E=Sophos;i="5.97,296,1669075200"; d="scan'208";a="181587568" Received: from pdx4-co-svc-p1-lb2-vlan3.amazon.com (HELO email-inbound-relay-pdx-2b-m6i4x-a893d89c.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 07:04:49 +0000 Received: from EX13MTAUWB001.ant.amazon.com (pdx1-ws-svc-p6-lb9-vlan2.pdx.amazon.com [10.236.137.194]) by email-inbound-relay-pdx-2b-m6i4x-a893d89c.us-west-2.amazon.com (Postfix) with ESMTPS id 58F3041410; Tue, 14 Feb 2023 07:04:48 +0000 (UTC) Received: from EX19D010UWA004.ant.amazon.com (10.13.138.204) by EX13MTAUWB001.ant.amazon.com (10.43.161.249) with Microsoft SMTP Server (TLS) id 15.0.1497.45; Tue, 14 Feb 2023 07:04:47 +0000 Received: from u9aa42af9e4c55a.ant.amazon.com (10.43.162.56) by EX19D010UWA004.ant.amazon.com (10.13.138.204) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.1118.24; Tue, 14 Feb 2023 07:04:47 +0000 From: Munehisa Kamata To: CC: , , , , , , , Subject: [PATCH v2] sched/psi: fix use-after-free in ep_remove_wait_queue() Date: Mon, 13 Feb 2023 23:04:29 -0800 Message-ID: <20230214070429.3613260-1-kamatam@amazon.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 X-Originating-IP: [10.43.162.56] X-ClientProxiedBy: EX13D36UWB001.ant.amazon.com (10.43.161.84) To EX19D010UWA004.ant.amazon.com (10.13.138.204) X-Spam-Status: No, score=-11.9 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_SPF_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1756686839296989708?= X-GMAIL-MSGID: =?utf-8?q?1757789439194648770?= 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 without clearing the queue and reference 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 can keep having the last reference to the pressure file that is tied to the freed waitqueue until explicit close or exit later. fput ep_eventpoll_release ep_free ep_remove_wait_queue remove_wait_queue Then, the thread accesses to the already-freed waitqueue when dropping the reference and results in use-after-free as pasted below. The fundamental problem here is that the lifetime of the waitqueue is not tied to the file's real lifetime as shown above. Using wake_up_pollfree() here might be less than ideal, but it also is not fully contradicting 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 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 --- 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..6e66c15f6450 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 otherwise. */ - wake_up_interruptible(&t->event_wait); + wake_up_pollfree(&t->event_wait); mutex_lock(&group->trigger_lock);