diff options
| author | Eric Dumazet <edumazet@google.com> | 2023-11-09 17:48:59 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2023-11-13 20:51:37 -0800 |
| commit | 73bde5a3294853947252cd9092a3517c7cb0cd2d (patch) | |
| tree | b10fc69b8c99caf44ac193dc0cf9bb8e92e3633d /drivers/ptp/ptp_private.h | |
| parent | 4b3812d90b2c93723adf4b6ce99240d301f7d5f9 (diff) | |
| download | lwn-73bde5a3294853947252cd9092a3517c7cb0cd2d.tar.gz lwn-73bde5a3294853947252cd9092a3517c7cb0cd2d.zip | |
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/ptp_private.h')
| -rw-r--r-- | drivers/ptp/ptp_private.h | 8 |
1 files changed, 6 insertions, 2 deletions
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; } |