From nobody Mon Oct 6 15:15:52 2025 Received: from mail-pg1-f180.google.com (mail-pg1-f180.google.com [209.85.215.180]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B132179CD; Sat, 19 Jul 2025 12:40:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.180 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752928848; cv=none; b=oWa/63gNYBvBFeU1F8HdB98jvrAJMqfhokmeiZUHsJjcEA0jM9VVVhI/2IDOOTy8TDk0xsEACfN0purlN82LziDlpw3XvIrEpNiAY09aDbdk6z2WetngoQ8sODPUra2jh330ejzmUC0WGXRxJlPZ3ZZB3kld9w/9TunNsADGLZQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1752928848; c=relaxed/simple; bh=POOKiELi+GdlAqJjsQHw6ZyuOJyr7R8My1xl6e7qJ0g=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=lk7Gsk27BsbodnHil4U6C17XDJned4YmGOC8p/sdK8+EV5ARv2EaP0b2u/SI5hvkNqU/eLUImYRFcrSjTXYs/4EVPWVlA96Flwu+2ItCmPlCQar37lkG9NlJ+syih3oP9At1+TiaK7NcQKHxu4RE+vNtTFJsX3YtLa+w6GuCeSk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=BxCigReU; arc=none smtp.client-ip=209.85.215.180 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="BxCigReU" Received: by mail-pg1-f180.google.com with SMTP id 41be03b00d2f7-b271f3ae786so2184101a12.3; Sat, 19 Jul 2025 05:40:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1752928846; x=1753533646; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=BQfdgdkRBWe5TVjNpBGDG5q7sQM2q/hqv2mJrxoFnZQ=; b=BxCigReUdN7dIgRQJVxIvS20L1G2XAnlpkCpFOv32hIV0hKqttOYdZAafsjuEAhoGo lOmmsmT8V7iSt/VBrX5vAJYClS5NTlvsbJMmEiLK0atWHMZJ6H5OmUJ+tmLZyUuPgXuR mnxrJoSmNw2ajVC1sVwxUmOWbEs4Gk7THt6L/0AdoDOmSyUM/qhB6lwiTkXJTDt5LdgE MSpDOLw7MsdlUwLtWBNyKpX7Z666Apuno+J43GnSYinNczOCak1DX5T3gEsjxyE+U2ri 64q7AZwmccke8G1DfF4+0YinFbk1hUA4JIrYVcit34HYYO/nHNvNsBvo23qy1N3gjnau WxgQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1752928846; x=1753533646; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=BQfdgdkRBWe5TVjNpBGDG5q7sQM2q/hqv2mJrxoFnZQ=; b=HsiH5spRHQrVRSYwss55q411W7jGAyZ9Ai7YzoS+Gx0xY56BMYwsC5NxDwM0ua8dRi h6maybw4UWO3YmcHH7qrkPKi1Nr+qqPmrfaNPRRGwc/Fk47pVzjcvJH0hsuiIz6Bkf0z 8swyI4NYJyCONaqybnXPLAt2+bM0fqtfdDRH6vbsoIAaed5kJJd4PHvDJA8b1J3v4qmL uF7uWBrMypNFVouYRP9JSOLvuX7mwGNAKz8W+6yylw6UewPkP9wPDhBZIkp4QcjsJjbV 0oxRMgwwApVAu8WSRsdsRg/GMReAwVnAELzIydF6Gf2t3Ycgpn9TPa9SbzUW30OEtHLh hBVw== X-Forwarded-Encrypted: i=1; AJvYcCVd0qciO5fg1sqRO3uHCTz+nd/fMZy67kACzVGSnJUdSMXQu791RdbN29PPjVVsZX6jOzCAc1LotVxxmTM=@vger.kernel.org, AJvYcCWZmfSMyJ/trXG+eT2YQ3KlDxndHuVDBUHrOY2H1m7aYNYRjKkCOTDYandTzMwHnEsLyhR4FEwn@vger.kernel.org X-Gm-Message-State: AOJu0Yyzq6dIqT3Y7RMSl+1B7Y7XNv1OyLAB6Csx7GDz7NCaufO+sRVU BkurK/XzYFFVAsOig8zCB4fYJyVNeRrldDTzatHfW4uiSIonpZOGg5Jg X-Gm-Gg: ASbGnctw0gHmgdFpR2A2hG98o7yN3P7RGWau9WwIcGRsFJGOBje9r2ffGD+fOp5XxLm Mc0Mrspd+o5+B4JwUbG5CLvBykpReq2qUzkB0P9/xpwcVOSnxn3y7fSuIwD6r+6nF56/dgVut2y QSTtIwMcpOtnR89A+9c99ahy8NicES/jmdDqOQQI/o9AZRki6kYHHdwZcY0BcdvwBuTyNLZoUQH zdCNjRB+L+TL0mdQyvHHGlkW9du+ogGY6pJu9RqpC4bUuWCSGZCK1NmsS+oMYbXT6dRNfRU7Xo8 oX058Zcz6qBnhrXDQsL4IdwvH82jVH1p0XbHpwJvvVIj1b1OONIm9p3WqGNOaIemNJM+Ly7ODft ULlBgbUWW1D45nGbt0cNAtGSm00guA3Y+emhFCbJslOfh7GzcIQ== X-Google-Smtp-Source: AGHT+IGJLabOuao1TExGeMbmwrpLcuQArmlji57Wwb1no1QTxnH0aii27+o4KkJ3Xa0K2e34n4iFGw== X-Received: by 2002:a17:90b:5289:b0:315:af43:12ee with SMTP id 98e67ed59e1d1-31c9e761501mr23718931a91.16.1752928845850; Sat, 19 Jul 2025 05:40:45 -0700 (PDT) Received: from name2965-Precision-7820-Tower.. ([121.185.186.233]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-31cc3f44970sm2985883a91.39.2025.07.19.05.40.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 19 Jul 2025 05:40:44 -0700 (PDT) From: Jeongjun Park To: richardcochran@gmail.com Cc: andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, yangbo.lu@nxp.com, vladimir.oltean@nxp.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+7cfb66a237c4a5fb22ad@syzkaller.appspotmail.com, Jeongjun Park Subject: [PATCH net v3] ptp: prevent possible ABBA deadlock in ptp_clock_freerun() Date: Sat, 19 Jul 2025 21:40:22 +0900 Message-Id: <20250719124022.1536524-1-aha310510@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" syzbot reported the following ABBA deadlock: CPU0 CPU1 ---- ---- n_vclocks_store() lock(&ptp->n_vclocks_mux) [1] (physical clock) pc_clock_adjtime() lock(&clk->rwsem) [2] (physical clock) ... ptp_clock_freerun() ptp_vclock_in_use() lock(&ptp->n_vclocks_mux) [3] (physical clock) ptp_clock_unregister() posix_clock_unregister() lock(&clk->rwsem) [4] (virtual clock) Functions like clock_adjtime() can only be called with physical clocks. Therefore, all structures used in this function are physical clocks. However, when unregistering vclocks in n_vclocks_store(), ptp->n_vclocks_mux is a physical clock lock, but clk->rwsem of ptp_clock_unregister() called through device_for_each_child_reverse() is a virtual clock lock. Therefore, clk->rwsem used in CPU0 and clk->rwsem used in CPU1 are different locks, but in lockdep, a false positive occurs because the possibility of deadlock is determined through lock-class. Therefore, to prevent such false positive in lockdep, a subclass annotation must be added to the lock used in the virtual clock structure. Reported-by: syzbot+7cfb66a237c4a5fb22ad@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D7cfb66a237c4a5fb22ad Fixes: 73f37068d540 ("ptp: support ptp physical/virtual clocks conversion") Signed-off-by: Jeongjun Park --- v3: Annotate lock subclass to prevent false positives of lockdep - Link to v2: https://lore.kernel.org/all/20250718114958.1473199-1-aha31051= 0@gmail.com/ v2: Add CC Vladimir - Link to v1: https://lore.kernel.org/all/20250705145031.140571-1-aha310510= @gmail.com/ --- drivers/ptp/ptp_private.h | 5 +++++ drivers/ptp/ptp_vclock.c | 16 ++++++++++++++++ 2 files changed, 21 insertions(+) diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h index a6aad743c282..b352df4cd3f9 100644 --- a/drivers/ptp/ptp_private.h +++ b/drivers/ptp/ptp_private.h @@ -24,6 +24,11 @@ #define PTP_DEFAULT_MAX_VCLOCKS 20 #define PTP_MAX_CHANNELS 2048 =20 +enum { + PTP_LOCK_PHYSICAL =3D 0, + PTP_LOCK_VIRTUAL, +}; + struct timestamp_event_queue { struct ptp_extts_event buf[PTP_MAX_TIMESTAMPS]; int head; diff --git a/drivers/ptp/ptp_vclock.c b/drivers/ptp/ptp_vclock.c index 7febfdcbde8b..b16c66c254ae 100644 --- a/drivers/ptp/ptp_vclock.c +++ b/drivers/ptp/ptp_vclock.c @@ -154,6 +154,20 @@ static long ptp_vclock_refresh(struct ptp_clock_info *= ptp) return PTP_VCLOCK_REFRESH_INTERVAL; } =20 +#ifdef CONFIG_LOCKDEP +static void ptp_vclock_set_subclass(struct ptp_clock *ptp) +{ + lockdep_set_subclass(&ptp->n_vclocks_mux, PTP_LOCK_VIRTUAL); + lockdep_set_subclass(&ptp->clock.rwsem, PTP_LOCK_VIRTUAL); + lockdep_set_subclass(&ptp->tsevqs_lock, PTP_LOCK_VIRTUAL); + lockdep_set_subclass(&ptp->pincfg_mux, PTP_LOCK_VIRTUAL); +} +#else +static void ptp_vclock_set_subclass(struct ptp_clock *ptp) +{ +} +#endif + static const struct ptp_clock_info ptp_vclock_info =3D { .owner =3D THIS_MODULE, .name =3D "ptp virtual clock", @@ -213,6 +227,8 @@ struct ptp_vclock *ptp_vclock_register(struct ptp_clock= *pclock) return NULL; } =20 + ptp_vclock_set_subclass(vclock->clock); + timecounter_init(&vclock->tc, &vclock->cc, 0); ptp_schedule_worker(vclock->clock, PTP_VCLOCK_REFRESH_INTERVAL); =20 --