From mboxrd@z Thu Jan 1 00:00:00 1970 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 802D0C3DA7D for ; Wed, 28 Dec 2022 16:39:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233695AbiL1QjN (ORCPT ); Wed, 28 Dec 2022 11:39:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60786 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235093AbiL1Qii (ORCPT ); Wed, 28 Dec 2022 11:38:38 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5779C1C427 for ; Wed, 28 Dec 2022 08:34:10 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id E19AF61562 for ; Wed, 28 Dec 2022 16:34:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02A36C433D2; Wed, 28 Dec 2022 16:34:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1672245249; bh=+aXCmwXs+uqOZ1eRtgmRmSNmXqLTFfjXkgefY15ukC0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=2I3F8icU8rhpdJPoCAPbt7jFeVV3UR8q6i1B9YPLMyzzr9aG5rIg/9HYdUF0eHQC4 lKrW7qJ7YtQEpp7hXNxkgn7ctl0Dbc0vD1QzrH9HeifdlLTisyo4a+r7qWsMVGLDHU mSaVONatZ4LcOeXcUAWV7vITYnsqf+t62ZJcTU2o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Maksim Kiselev , Vladimir Oltean , Paolo Abeni , Sasha Levin Subject: [PATCH 6.0 0860/1073] net: dsa: mv88e6xxx: avoid reg_lock deadlock in mv88e6xxx_setup_port() Date: Wed, 28 Dec 2022 15:40:48 +0100 Message-Id: <20221228144351.378690278@linuxfoundation.org> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20221228144328.162723588@linuxfoundation.org> References: <20221228144328.162723588@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Vladimir Oltean [ Upstream commit a7d82367daa6baa5e8399e6327e7f2f463534505 ] In the blamed commit, it was not noticed that one implementation of chip->info->ops->phylink_get_caps(), called by mv88e6xxx_get_caps(), may access hardware registers, and in doing so, it takes the mv88e6xxx_reg_lock(). Namely, this is mv88e6352_phylink_get_caps(). This is a problem because mv88e6xxx_get_caps(), apart from being a top-level function (method invoked by dsa_switch_ops), is now also directly called from mv88e6xxx_setup_port(), which runs under the mv88e6xxx_reg_lock() taken by mv88e6xxx_setup(). Therefore, when running on mv88e6352, the reg_lock would be acquired a second time and the system would deadlock on driver probe. The things that mv88e6xxx_setup() can compete with in terms of register access with are the IRQ handlers and MDIO bus operations registered by mv88e6xxx_probe(). So there is a real need to acquire the register lock. The register lock can, in principle, be dropped and re-acquired pretty much at will within the driver, as long as no operations that involve waiting for indirect access to complete (essentially, callers of mv88e6xxx_smi_direct_wait() and mv88e6xxx_wait_mask()) are interrupted with the lock released. However, I would guess that in mv88e6xxx_setup(), the critical section is kept open for such a long time just in order to optimize away multiple lock/unlock operations on the registers. We could, in principle, drop the reg_lock right before the mv88e6xxx_setup_port() -> mv88e6xxx_get_caps() call, and re-acquire it immediately afterwards. But this would look ugly, because mv88e6xxx_setup_port() would release a lock which it didn't acquire, but the caller did. A cleaner solution to this issue comes from the observation that struct mv88e6xxxx_ops methods generally assume they are called with the reg_lock already acquired. Whereas mv88e6352_phylink_get_caps() is more the exception rather than the norm, in that it acquires the lock itself. Let's enforce the same locking pattern/convention for chip->info->ops->phylink_get_caps() as well, and make mv88e6xxx_get_caps(), the top-level function, acquire the register lock explicitly, for this one implementation that will access registers for port 4 to work properly. This means that mv88e6xxx_setup_port() will no longer call the top-level function, but the low-level mv88e6xxx_ops method which expects the correct calling context (register lock held). Compared to chip->info->ops->phylink_get_caps(), mv88e6xxx_get_caps() also fixes up the supported_interfaces bitmap for internal ports, since that can be done generically and does not require per-switch knowledge. That's code which will no longer execute, however mv88e6xxx_setup_port() doesn't need that. It just needs to look at the mac_capabilities bitmap. Fixes: cc1049ccee20 ("net: dsa: mv88e6xxx: fix speed setting for CPU/DSA ports") Reported-by: Maksim Kiselev Signed-off-by: Vladimir Oltean Tested-by: Maksim Kiselev Link: https://lore.kernel.org/r/20221214110120.3368472-1-vladimir.oltean@nxp.com Signed-off-by: Paolo Abeni Signed-off-by: Sasha Levin --- drivers/net/dsa/mv88e6xxx/chip.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c index 546d90dae933..0fd978e3ce2d 100644 --- a/drivers/net/dsa/mv88e6xxx/chip.c +++ b/drivers/net/dsa/mv88e6xxx/chip.c @@ -689,13 +689,12 @@ static void mv88e6352_phylink_get_caps(struct mv88e6xxx_chip *chip, int port, /* Port 4 supports automedia if the serdes is associated with it. */ if (port == 4) { - mv88e6xxx_reg_lock(chip); err = mv88e6352_g2_scratch_port_has_serdes(chip, port); if (err < 0) dev_err(chip->dev, "p%d: failed to read scratch\n", port); if (err <= 0) - goto unlock; + return; cmode = mv88e6352_get_port4_serdes_cmode(chip); if (cmode < 0) @@ -703,8 +702,6 @@ static void mv88e6352_phylink_get_caps(struct mv88e6xxx_chip *chip, int port, port); else mv88e6xxx_translate_cmode(cmode, supported); -unlock: - mv88e6xxx_reg_unlock(chip); } } @@ -823,7 +820,9 @@ static void mv88e6xxx_get_caps(struct dsa_switch *ds, int port, { struct mv88e6xxx_chip *chip = ds->priv; + mv88e6xxx_reg_lock(chip); chip->info->ops->phylink_get_caps(chip, port, config); + mv88e6xxx_reg_unlock(chip); if (mv88e6xxx_phy_is_internal(ds, port)) { __set_bit(PHY_INTERFACE_MODE_INTERNAL, @@ -3299,7 +3298,7 @@ static int mv88e6xxx_setup_port(struct mv88e6xxx_chip *chip, int port) struct phylink_config pl_config = {}; unsigned long caps; - mv88e6xxx_get_caps(ds, port, &pl_config); + chip->info->ops->phylink_get_caps(chip, port, &pl_config); caps = pl_config.mac_capabilities; -- 2.35.1