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authorEric Dumazet <edumazet@google.com>2023-11-09 20:48:59 +0300
committerJakub Kicinski <kuba@kernel.org>2023-11-14 07:51:37 +0300
commit73bde5a3294853947252cd9092a3517c7cb0cd2d (patch)
treeb10fc69b8c99caf44ac193dc0cf9bb8e92e3633d /drivers/ptp
parent4b3812d90b2c93723adf4b6ce99240d301f7d5f9 (diff)
downloadlinux-73bde5a3294853947252cd9092a3517c7cb0cd2d.tar.xz
ptp: annotate data-race around q->head and q->tail
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 <edumazet@google.com> Acked-by: Richard Cochran <richardcochran@gmail.com> Link: https://lore.kernel.org/r/20231109174859.3995880-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'drivers/ptp')
-rw-r--r--drivers/ptp/ptp_chardev.c3
-rw-r--r--drivers/ptp/ptp_clock.c5
-rw-r--r--drivers/ptp/ptp_private.h8
-rw-r--r--drivers/ptp/ptp_sysfs.c3
4 files changed, 13 insertions, 6 deletions
diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index 3f7a74788802..7513018c9f9a 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -572,7 +572,8 @@ ssize_t ptp_read(struct posix_clock_context *pccontext, uint rdflags,
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 3134568af622..15b804ba4868 100644
--- a/drivers/ptp/ptp_clock.c
+++ b/drivers/ptp/ptp_clock.c
@@ -57,10 +57,11 @@ 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 35fde0a05746..45f9002a5dca 100644
--- a/drivers/ptp/ptp_private.h
+++ b/drivers/ptp/ptp_private.h
@@ -85,9 +85,13 @@ struct ptp_vclock {
* 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 7d023d9d0acb..f7a499a1bd39 100644
--- a/drivers/ptp/ptp_sysfs.c
+++ b/drivers/ptp/ptp_sysfs.c
@@ -94,7 +94,8 @@ 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);