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 8194139FE1; Fri, 24 Nov 2023 17:58:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="zIFf1xnh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E9145C433C8; Fri, 24 Nov 2023 17:58:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1700848733; bh=FjjdDm14ozEdMXMl0ZnQYUWAR2A0lGZX7X4eVi6s+2I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zIFf1xnh7rkIS+Irzo7gSwf7kqe8VZvGok1KEgpgvkOyktjNpwg43lV1OqPneGStT 2a/UeMrcSsAXw06i5jn6gTg34Oz2h+Dxwud+knMItdV2txwDfuZQYtfnLRf9LN4msm emXnQ6cLP5wtBJGpAC726IIFcWnxoEIM3k+sKljc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Eric Dumazet , Richard Cochran , Jakub Kicinski , Sasha Levin Subject: [PATCH 4.19 42/97] ptp: annotate data-race around q->head and q->tail Date: Fri, 24 Nov 2023 17:50:15 +0000 Message-ID: <20231124171935.718234728@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231124171934.122298957@linuxfoundation.org> References: <20231124171934.122298957@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit 73bde5a3294853947252cd9092a3517c7cb0cd2d ] As I was working on a syzbot report, I found that KCSAN would probably complain that reading q->head or q->tail without barriers could lead to invalid results. Add corresponding READ_ONCE() and WRITE_ONCE() to avoid load-store tearing. Fixes: d94ba80ebbea ("ptp: Added a brand new class driver for ptp clocks.") Signed-off-by: Eric Dumazet Acked-by: Richard Cochran Link: https://lore.kernel.org/r/20231109174859.3995880-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/ptp/ptp_chardev.c | 3 ++- drivers/ptp/ptp_clock.c | 5 +++-- drivers/ptp/ptp_private.h | 8 ++++++-- drivers/ptp/ptp_sysfs.c | 3 ++- 4 files changed, 13 insertions(+), 6 deletions(-) diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c index 796eeffdf93b1..8ff2dd5c52e64 100644 --- a/drivers/ptp/ptp_chardev.c +++ b/drivers/ptp/ptp_chardev.c @@ -346,7 +346,8 @@ ssize_t ptp_read(struct posix_clock *pc, for (i = 0; i < cnt; i++) { event[i] = queue->buf[queue->head]; - queue->head = (queue->head + 1) % PTP_MAX_TIMESTAMPS; + /* Paired with READ_ONCE() in queue_cnt() */ + WRITE_ONCE(queue->head, (queue->head + 1) % PTP_MAX_TIMESTAMPS); } spin_unlock_irqrestore(&queue->lock, flags); diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c index 89632cc9c28fc..1e92bd897aa45 100644 --- a/drivers/ptp/ptp_clock.c +++ b/drivers/ptp/ptp_clock.c @@ -68,10 +68,11 @@ static void enqueue_external_timestamp(struct timestamp_event_queue *queue, dst->t.sec = seconds; dst->t.nsec = remainder; + /* Both WRITE_ONCE() are paired with READ_ONCE() in queue_cnt() */ if (!queue_free(queue)) - queue->head = (queue->head + 1) % PTP_MAX_TIMESTAMPS; + WRITE_ONCE(queue->head, (queue->head + 1) % PTP_MAX_TIMESTAMPS); - queue->tail = (queue->tail + 1) % PTP_MAX_TIMESTAMPS; + WRITE_ONCE(queue->tail, (queue->tail + 1) % PTP_MAX_TIMESTAMPS); spin_unlock_irqrestore(&queue->lock, flags); } diff --git a/drivers/ptp/ptp_private.h b/drivers/ptp/ptp_private.h index 05f6b6a9bbd58..1e02b5ae6127b 100644 --- a/drivers/ptp/ptp_private.h +++ b/drivers/ptp/ptp_private.h @@ -68,9 +68,13 @@ struct ptp_clock { * that a writer might concurrently increment the tail does not * matter, since the queue remains nonempty nonetheless. */ -static inline int queue_cnt(struct timestamp_event_queue *q) +static inline int queue_cnt(const struct timestamp_event_queue *q) { - int cnt = q->tail - q->head; + /* + * Paired with WRITE_ONCE() in enqueue_external_timestamp(), + * ptp_read(), extts_fifo_show(). + */ + int cnt = READ_ONCE(q->tail) - READ_ONCE(q->head); return cnt < 0 ? PTP_MAX_TIMESTAMPS + cnt : cnt; } diff --git a/drivers/ptp/ptp_sysfs.c b/drivers/ptp/ptp_sysfs.c index f97a5eefa2e23..b9e2f08960688 100644 --- a/drivers/ptp/ptp_sysfs.c +++ b/drivers/ptp/ptp_sysfs.c @@ -91,7 +91,8 @@ static ssize_t extts_fifo_show(struct device *dev, qcnt = queue_cnt(queue); if (qcnt) { event = queue->buf[queue->head]; - queue->head = (queue->head + 1) % PTP_MAX_TIMESTAMPS; + /* Paired with READ_ONCE() in queue_cnt() */ + WRITE_ONCE(queue->head, (queue->head + 1) % PTP_MAX_TIMESTAMPS); } spin_unlock_irqrestore(&queue->lock, flags); -- 2.42.0