From patchwork Wed May 11 06:19:51 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qi Zheng X-Patchwork-Id: 12845830 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8699EC433EF for ; Wed, 11 May 2022 06:20:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0F2176B0073; Wed, 11 May 2022 02:20:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 09FBD8D0002; Wed, 11 May 2022 02:20:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E83DB6B007D; Wed, 11 May 2022 02:20:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id DC1336B0073 for ; Wed, 11 May 2022 02:20:15 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id C04B3322C2 for ; Wed, 11 May 2022 06:20:15 +0000 (UTC) X-FDA: 79452462390.26.6D04EE8 Received: from mail-pg1-f175.google.com (mail-pg1-f175.google.com [209.85.215.175]) by imf15.hostedemail.com (Postfix) with ESMTP id 2CAB5A009A for ; Wed, 11 May 2022 06:20:03 +0000 (UTC) Received: by mail-pg1-f175.google.com with SMTP id 7so914045pga.12 for ; Tue, 10 May 2022 23:20:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=P6VNAwCH3n0ix/X7qN1lMdQqsfuBwClntHRvqIjUObk=; b=TWy8cyml379D9laFnVPycgxdVd2TTLlXmCcqmId+QI2tzj4kUZHMdFsHw73Xh/+MlQ uPoZIIF9qAD+Iy7mN73nKAxSP/ZRtyp6YLUmJaZ39zkudrUVv0kUL8b1nhjkFKjk+6vl 6orErtugJO4H1+Gy3ji1Fk2ICNy+LAWsm2v3sQYFL3L3IoGRtdwCW6HsbXBi9I2TEdwa ChF+xMVYEooN/85OtqwPVR/Nb82CVe8JJwgPOAoxFHC9oXb3aeVv0bfNlNsaytuCJRHI pCKEPjppXWU2vgzkZ7UnD2eJGlo/o4Wg1BPfXOJO5YxGm1oHhHBaYnV2s1CrMFBOc854 1GYQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=P6VNAwCH3n0ix/X7qN1lMdQqsfuBwClntHRvqIjUObk=; b=O/VqBaCeEv4gjgYjqmX1N1aGqc3R+YWjcO6V6GggMSA/dWbdX5rJfgYN62pFZboXzp bV1a1LateNawKKNqdUjuosoRnoHJtajyJ/GelAtDntS2vicJmydU7XFo+8aqBQGDEhlK Crgi4LG7uLT7b6vzBC2QSRFyXr1vlOdYuvQEOHbE9YM11hXIEA1EbEAD66CzrtX5zAU1 l2TcWVL48gFpbgiVjaFcE7fmoKx01AtX92jS5jEqW9Mg93SE2YxRxg9fdLE3lnFMwPW8 BSOWR0H4NEvuH8SrXasMdWcgBUNXYCpp1Zh4KHXE7w1LBkDPhbnk4UVTp5El4aIy0llV wsag== X-Gm-Message-State: AOAM531On7e0+RWZ7jgJaoj2LHWblacnVRADbuV0gZloW1EJcgBWSIot pa+y9Hy5JRp/ee47vM9FqOYiim2fTJcvsg== X-Google-Smtp-Source: ABdhPJyyDckfPI4haYh0t1Eo1lwNryAkpm9KBeuy7gA6mj5GpQeczY+jgQs0trOIfRO6E3LmQG9J7g== X-Received: by 2002:a62:1490:0:b0:4cc:3c7d:4dec with SMTP id 138-20020a621490000000b004cc3c7d4decmr5258576pfu.32.1652250014402; Tue, 10 May 2022 23:20:14 -0700 (PDT) Received: from C02DW0BEMD6R.bytedance.net ([139.177.225.242]) by smtp.gmail.com with ESMTPSA id be12-20020a170902aa0c00b0015e8d4eb1e4sm771500plb.46.2022.05.10.23.20.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 May 2022 23:20:13 -0700 (PDT) From: Qi Zheng To: akpm@linux-foundation.org, jirislaby@kernel.org, akinobu.mita@gmail.com, vbabka@suse.cz, gregkh@linuxfoundation.org, rostedt@goodmis.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Qi Zheng Subject: [PATCH v2 2/2] tty: fix deadlock caused by calling printk() under tty_port->lock Date: Wed, 11 May 2022 14:19:51 +0800 Message-Id: <20220511061951.1114-2-zhengqi.arch@bytedance.com> X-Mailer: git-send-email 2.24.3 (Apple Git-128) In-Reply-To: <20220511061951.1114-1-zhengqi.arch@bytedance.com> References: <20220511061951.1114-1-zhengqi.arch@bytedance.com> MIME-Version: 1.0 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 2CAB5A009A Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=TWy8cyml; spf=pass (imf15.hostedemail.com: domain of zhengqi.arch@bytedance.com designates 209.85.215.175 as permitted sender) smtp.mailfrom=zhengqi.arch@bytedance.com; dmarc=pass (policy=none) header.from=bytedance.com X-Rspam-User: X-Stat-Signature: 3ssq6qbcfoca6gj3ue8xrm6mb88eo5mw X-HE-Tag: 1652250003-471967 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The pty_write() invokes kmalloc() which may invoke a normal printk() to print failure message. This can cause a deadlock in the scenario reported by syz-bot below: CPU0 CPU1 CPU2 ---- ---- ---- lock(console_owner); lock(&port_lock_key); lock(&port->lock); lock(&port_lock_key); lock(&port->lock); lock(console_owner); As commit dbdda842fe96 ("printk: Add console owner and waiter logic to load balance console writes") said, such deadlock can be prevented by using printk_deferred() in kmalloc() (which is invoked in the section guarded by the port->lock). But there are too many printk() on the kmalloc() path, and kmalloc() can be called from anywhere, so changing printk() to printk_deferred() is too complicated and inelegant. Therefore, this patch chooses to specify __GFP_NOWARN to kmalloc(), so that printk() will not be called, and this deadlock problem can be avoided. Syz-bot reported the following lockdep error: ====================================================== WARNING: possible circular locking dependency detected 5.4.143-00237-g08ccc19a-dirty #10 Not tainted ------------------------------------------------------ syz-executor.4/29420 is trying to acquire lock: ffffffff8aedb2a0 (console_owner){....}-{0:0}, at: console_trylock_spinning kernel/printk/printk.c:1752 [inline] ffffffff8aedb2a0 (console_owner){....}-{0:0}, at: vprintk_emit+0x2ca/0x470 kernel/printk/printk.c:2023 but task is already holding lock: ffff8880119c9158 (&port->lock){-.-.}-{2:2}, at: pty_write+0xf4/0x1f0 drivers/tty/pty.c:120 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&port->lock){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159 tty_port_tty_get drivers/tty/tty_port.c:288 [inline] <-- lock(&port->lock); tty_port_default_wakeup+0x1d/0xb0 drivers/tty/tty_port.c:47 serial8250_tx_chars+0x530/0xa80 drivers/tty/serial/8250/8250_port.c:1767 serial8250_handle_irq.part.0+0x31f/0x3d0 drivers/tty/serial/8250/8250_port.c:1854 serial8250_handle_irq drivers/tty/serial/8250/8250_port.c:1827 [inline] <-- lock(&port_lock_key); serial8250_default_handle_irq+0xb2/0x220 drivers/tty/serial/8250/8250_port.c:1870 serial8250_interrupt+0xfd/0x200 drivers/tty/serial/8250/8250_core.c:126 __handle_irq_event_percpu+0x109/0xa50 kernel/irq/handle.c:156 [...] -> #1 (&port_lock_key){-.-.}-{2:2}: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline] _raw_spin_lock_irqsave+0x35/0x50 kernel/locking/spinlock.c:159 serial8250_console_write+0x184/0xa40 drivers/tty/serial/8250/8250_port.c:3198 <-- lock(&port_lock_key); call_console_drivers kernel/printk/printk.c:1819 [inline] console_unlock+0x8cb/0xd00 kernel/printk/printk.c:2504 vprintk_emit+0x1b5/0x470 kernel/printk/printk.c:2024 <-- lock(console_owner); vprintk_func+0x8d/0x250 kernel/printk/printk_safe.c:394 printk+0xba/0xed kernel/printk/printk.c:2084 register_console+0x8b3/0xc10 kernel/printk/printk.c:2829 univ8250_console_init+0x3a/0x46 drivers/tty/serial/8250/8250_core.c:681 console_init+0x49d/0x6d3 kernel/printk/printk.c:2915 start_kernel+0x5e9/0x879 init/main.c:713 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241 -> #0 (console_owner){....}-{0:0}: [...] lock_acquire+0x127/0x340 kernel/locking/lockdep.c:4734 console_trylock_spinning kernel/printk/printk.c:1773 [inline] <-- lock(console_owner); vprintk_emit+0x307/0x470 kernel/printk/printk.c:2023 vprintk_func+0x8d/0x250 kernel/printk/printk_safe.c:394 printk+0xba/0xed kernel/printk/printk.c:2084 fail_dump lib/fault-inject.c:45 [inline] should_fail+0x67b/0x7c0 lib/fault-inject.c:144 __should_failslab+0x152/0x1c0 mm/failslab.c:33 should_failslab+0x5/0x10 mm/slab_common.c:1224 slab_pre_alloc_hook mm/slab.h:468 [inline] slab_alloc_node mm/slub.c:2723 [inline] slab_alloc mm/slub.c:2807 [inline] __kmalloc+0x72/0x300 mm/slub.c:3871 kmalloc include/linux/slab.h:582 [inline] tty_buffer_alloc+0x23f/0x2a0 drivers/tty/tty_buffer.c:175 __tty_buffer_request_room+0x156/0x2a0 drivers/tty/tty_buffer.c:273 tty_insert_flip_string_fixed_flag+0x93/0x250 drivers/tty/tty_buffer.c:318 tty_insert_flip_string include/linux/tty_flip.h:37 [inline] pty_write+0x126/0x1f0 drivers/tty/pty.c:122 <-- lock(&port->lock); n_tty_write+0xa7a/0xfc0 drivers/tty/n_tty.c:2356 do_tty_write drivers/tty/tty_io.c:961 [inline] tty_write+0x512/0x930 drivers/tty/tty_io.c:1045 __vfs_write+0x76/0x100 fs/read_write.c:494 [...] other info that might help us debug this: Chain exists of: console_owner --> &port_lock_key --> &port->lock Fixes: b6da31b2c07c ("tty: Fix data race in tty_insert_flip_string_fixed_flag") Signed-off-by: Qi Zheng Acked-by: Jiri Slaby Acked-by: Greg Kroah-Hartman --- drivers/tty/tty_buffer.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index 646510476c30..bfa431a8e690 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -175,7 +175,8 @@ static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) */ if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit) return NULL; - p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); + p = kmalloc(sizeof(struct tty_buffer) + 2 * size, + GFP_ATOMIC | __GFP_NOWARN); if (p == NULL) return NULL;