diff options
| author | Eric Dumazet | 2023-11-09 17:48:59 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2023-11-28 17:07:05 +0000 |
| commit | f84846731b937bcb82ac998cc7e2e62325d0ecf9 (patch) | |
| tree | 0c0af5b5a3bec06c595fa04e4ac9dc60e0722efe | |
| parent | ceae93d76a51855aafa85b02e05f02a0f3eacc66 (diff) | |
ptp: annotate data-race around q->head and q->tail
[ 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 <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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | drivers/ptp/ptp_chardev.c | 3 | ||||
| -rw-r--r-- | drivers/ptp/ptp_clock.c | 5 | ||||
| -rw-r--r-- | drivers/ptp/ptp_private.h | 8 | ||||
| -rw-r--r-- | 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 af3bc65c4595..9311f3d09c8f 100644 --- a/drivers/ptp/ptp_chardev.c +++ b/drivers/ptp/ptp_chardev.c @@ -487,7 +487,8 @@ 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 51cae72bb6db..3c3e4fbefeba 100644 --- a/drivers/ptp/ptp_clock.c +++ b/drivers/ptp/ptp_clock.c @@ -56,10 +56,11 @@ 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 75f58fc468a7..b8d4f61f14be 100644 --- a/drivers/ptp/ptp_private.h +++ b/drivers/ptp/ptp_private.h @@ -76,9 +76,13 @@ 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 f30b0a439470..74b9c794d636 100644 --- a/drivers/ptp/ptp_sysfs.c +++ b/drivers/ptp/ptp_sysfs.c @@ -79,7 +79,8 @@ 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); |