From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 97D6D250EA for ; Mon, 6 Nov 2023 13:34:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="ngsYktN8" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0AFAAC433C7; Mon, 6 Nov 2023 13:34:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1699277662; bh=Z7hRm13q043A8WyFFZFaDMHNvog4Ik3dhtMoiLBxEx4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ngsYktN8u6wZdNuekIvkFlKhQzCItBI+IoKSJvJKaAwvQKHbJjyyNGT0kQnDuGT6Y whlprx2LJDhpQQLv5n3PEDAoKoBChq+h6tklW92i5vcp44+pqXpP3IOwiw6FIe6uHQ ItaXBoArqGZC3RgtH/tpipiXA2TTn+KgpGC2zcUk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "linux-can@vger.kernel.org, lukas.magel@posteo.net, patches@lists.linux.dev, maxime.jayat@mobile-devices.fr, mkl@pengutronix.de, michal.sojka@cvut.cz, Oliver Hartkopp" , Maxime Jayat , Lukas Magel , Marc Kleine-Budde , Sasha Levin , Oliver Hartkopp Subject: [PATCH 5.10 87/95] can: isotp: isotp_sendmsg(): fix TX state detection and wait behavior Date: Mon, 6 Nov 2023 14:04:55 +0100 Message-ID: <20231106130307.879339728@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231106130304.678610325@linuxfoundation.org> References: <20231106130304.678610325@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lukas Magel [ Upstream commit d9c2ba65e651467de739324d978b04ed8729f483 ] With patch [1], isotp_poll was updated to also queue the poller in the so->wait queue, which is used for send state changes. Since the queue now also contains polling tasks that are not interested in sending, the queue fill state can no longer be used as an indication of send readiness. As a consequence, nonblocking writes can lead to a race and lock-up of the socket if there is a second task polling the socket in parallel. With this patch, isotp_sendmsg does not consult wq_has_sleepers but instead tries to atomically set so->tx.state and waits on so->wait if it is unable to do so. This behavior is in alignment with isotp_poll, which also checks so->tx.state to determine send readiness. V2: - Revert direct exit to goto err_event_drop [1] https://lore.kernel.org/all/20230331125511.372783-1-michal.sojka@cvut.cz Reported-by: Maxime Jayat Closes: https://lore.kernel.org/linux-can/11328958-453f-447f-9af8-3b5824dfb041@munic.io/ Signed-off-by: Lukas Magel Reviewed-by: Oliver Hartkopp Fixes: 79e19fa79cb5 ("can: isotp: isotp_ops: fix poll() to not report false EPOLLOUT events") Link: https://github.com/pylessard/python-udsoncan/issues/178#issuecomment-1743786590 Link: https://lore.kernel.org/all/20230827092205.7908-1-lukas.magel@posteo.net Signed-off-by: Marc Kleine-Budde Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- net/can/isotp.c | 19 ++++++++----------- 1 file changed, 8 insertions(+), 11 deletions(-) --- a/net/can/isotp.c +++ b/net/can/isotp.c @@ -925,21 +925,18 @@ static int isotp_sendmsg(struct socket * if (!so->bound || so->tx.state == ISOTP_SHUTDOWN) return -EADDRNOTAVAIL; -wait_free_buffer: - /* we do not support multiple buffers - for now */ - if (wq_has_sleeper(&so->wait) && (msg->msg_flags & MSG_DONTWAIT)) - return -EAGAIN; + while (cmpxchg(&so->tx.state, ISOTP_IDLE, ISOTP_SENDING) != ISOTP_IDLE) { + /* we do not support multiple buffers - for now */ + if (msg->msg_flags & MSG_DONTWAIT) + return -EAGAIN; - /* wait for complete transmission of current pdu */ - err = wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE); - if (err) - goto err_event_drop; - - if (cmpxchg(&so->tx.state, ISOTP_IDLE, ISOTP_SENDING) != ISOTP_IDLE) { if (so->tx.state == ISOTP_SHUTDOWN) return -EADDRNOTAVAIL; - goto wait_free_buffer; + /* wait for complete transmission of current pdu */ + err = wait_event_interruptible(so->wait, so->tx.state == ISOTP_IDLE); + if (err) + goto err_event_drop; } if (!size || size > MAX_MSG_LENGTH) {