From patchwork Tue May 10 11:38:09 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qi Zheng X-Patchwork-Id: 12844901 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 A3B44C433EF for ; Tue, 10 May 2022 11:38:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2ADC96B0073; Tue, 10 May 2022 07:38:49 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 25B726B0074; Tue, 10 May 2022 07:38:49 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0FCA26B0075; Tue, 10 May 2022 07:38:49 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 000E96B0073 for ; Tue, 10 May 2022 07:38:48 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id D4BCA1869 for ; Tue, 10 May 2022 11:38:48 +0000 (UTC) X-FDA: 79449636336.26.8133996 Received: from mail-pj1-f54.google.com (mail-pj1-f54.google.com [209.85.216.54]) by imf10.hostedemail.com (Postfix) with ESMTP id 855F0C003B for ; Tue, 10 May 2022 11:38:26 +0000 (UTC) Received: by mail-pj1-f54.google.com with SMTP id cq17-20020a17090af99100b001dc0386cd8fso1899244pjb.5 for ; Tue, 10 May 2022 04:38:48 -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=iMgJwS/SggrAADYtwStHw4r+a8CzDYa93UU0RlRB13g=; b=3hTdSoIkC2wRYFxclkOTIEfKDuHd679neMiuzW0MVKwy/2dUw4jCgZrwkoXVxijeqX wKkZnJ2HlrlRZveXZFSfFamIKk930Qa/rsBwrSp8opG+0hTqaYdJz2uURK6HunNd9EpL CJ/MDH+YvqvKGWYdVhb/NnapPZXJ39cf3LqO2h+TSso1wQxjXURQTxdl0shRMdkrQCYN rUM8YYI1cxOsjSyPRjM7EsyvkUnBnvV8Noubu128CSzAbexi4VbNisa1bOC8jZMGaI5V /NIQgh+jjKPYnU6RYqkjoRwf3bEdO28VwYzKZnn0ap/EtUx66bIvMPvfq0rfSH/vlmD/ v3MQ== 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=iMgJwS/SggrAADYtwStHw4r+a8CzDYa93UU0RlRB13g=; b=0wz9YzI1IRotCB0Q5V/1wHdyKT1fPeQdP5QfB0fbOKM8wsVUMaDjtpdRx8rCd4lyjd UXsUQ8bPYePo5TLH9CnAUW0fl1iurfw6SKKr6AFE85EAzBaouE/zIVeWC9gvGp5tPJ0a WOF8ucZdDRZk4tY/BgP+O4JSDDXFJhgPdUv8qyx6LT50Skg+Qrt2rkqvdSHn2ezZz8Av wVwQDORbOk0sCggCIpo5rflbkIlcb7Q5jy9kXlMj3UTNFhLO5oQfg9ogRG3XRDTLfgKy kT89U9U/yXoPWAets6mN4nfQr7LcIllaOLTpbtBvHqYz37xmJTFOTWglvDSX4byopKUH Pa9w== X-Gm-Message-State: AOAM5317mzZiEyehs6i4wyrGOajzTmi26CU45jrbiJxdLjlZKUT2gS2C 0JS+HB0PA01W40+xQokXn8GMrQ== X-Google-Smtp-Source: ABdhPJyn1xpQSL4/aHEcqOu8DmLsiNNCgfFUxwGhA8F+nSWNWQEYSr6bp/PUhnPPxKPL4kTdLYzEcw== X-Received: by 2002:a17:90b:17c3:b0:1dc:3f12:1dbc with SMTP id me3-20020a17090b17c300b001dc3f121dbcmr22651999pjb.169.1652182727333; Tue, 10 May 2022 04:38:47 -0700 (PDT) Received: from C02DW0BEMD6R.bytedance.net ([139.177.225.242]) by smtp.gmail.com with ESMTPSA id bj7-20020a170902850700b0015e8d4eb20bsm1800645plb.85.2022.05.10.04.38.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 May 2022 04:38:46 -0700 (PDT) From: Qi Zheng To: akinobu.mita@gmail.com, akpm@linux-foundation.org, vbabka@suse.cz, gregkh@linuxfoundation.org, jirislaby@kernel.org, rostedt@goodmis.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Qi Zheng Subject: [PATCH 2/2] tty: fix deadlock caused by calling printk() under tty_port->lock Date: Tue, 10 May 2022 19:38:09 +0800 Message-Id: <20220510113809.80626-2-zhengqi.arch@bytedance.com> X-Mailer: git-send-email 2.24.3 (Apple Git-128) In-Reply-To: <20220510113809.80626-1-zhengqi.arch@bytedance.com> References: <20220510113809.80626-1-zhengqi.arch@bytedance.com> MIME-Version: 1.0 X-Stat-Signature: twr6eugcoyu65a13tmkmdf896bncpp7f X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 855F0C003B X-Rspam-User: Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=bytedance-com.20210112.gappssmtp.com header.s=20210112 header.b=3hTdSoIk; dmarc=pass (policy=none) header.from=bytedance.com; spf=pass (imf10.hostedemail.com: domain of zhengqi.arch@bytedance.com designates 209.85.216.54 as permitted sender) smtp.mailfrom=zhengqi.arch@bytedance.com X-HE-Tag: 1652182706-467322 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 handle_irq_event_percpu+0x76/0x170 kernel/irq/handle.c:196 handle_irq_event+0xa1/0x130 kernel/irq/handle.c:213 handle_edge_irq+0x261/0xd00 kernel/irq/chip.c:833 generic_handle_irq_desc include/linux/irqdesc.h:156 [inline] do_IRQ+0xf2/0x2e0 arch/x86/kernel/irq.c:250 ret_from_intr+0x0/0x19 native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline] arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline] default_idle+0x2c/0x1a0 arch/x86/kernel/process.c:572 cpuidle_idle_call kernel/sched/idle.c:184 [inline] do_idle+0x44c/0x590 kernel/sched/idle.c:294 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:386 start_secondary+0x2d1/0x3e0 arch/x86/kernel/smpboot.c:264 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241 -> #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}: check_prev_add kernel/locking/lockdep.c:2600 [inline] check_prevs_add kernel/locking/lockdep.c:2705 [inline] validate_chain kernel/locking/lockdep.c:3095 [inline] __lock_acquire+0x27e6/0x4cc0 kernel/locking/lockdep.c:4200 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 vfs_write+0x268/0x5c0 fs/read_write.c:558 ksys_write+0x12d/0x250 fs/read_write.c:611 do_syscall_64+0xd7/0x380 arch/x86/entry/common.c:291 entry_SYSCALL_64_after_hwframe+0x49/0xbe 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 --- 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;