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authorEric Dumazet <edumazet@google.com>2023-11-09 20:48:59 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-11-28 20:19:51 +0300
commitc86085585de15a2e73697e6adfc86b5baa891fff (patch)
treeae8181d59079e699e064b6ce0748233aaa62fa22
parentb80056bd75a16e4550873ecefe12bc8fd190b1cf (diff)
downloadlinux-c86085585de15a2e73697e6adfc86b5baa891fff.tar.xz
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.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 362bf756e6b7..5a3a4cc0bec8 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -490,7 +490,8 @@ 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 80f74e38c2da..9a50bfb56453 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 6e4d5456a885..34ea5c16123a 100644
--- a/drivers/ptp/ptp_sysfs.c
+++ b/drivers/ptp/ptp_sysfs.c
@@ -90,7 +90,8 @@ 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);