[PATCH net] net: ena: PHC: Check return code before setting timestamp output

[Arthur Kiyanovski <akiyano@amazon.com>]

ena_phc_gettimex64() is setting the output parameter regardless
of whether ena_com_phc_get_timestamp() succeeded or failed.

When ena_com_phc_get_timestamp() returns an error, the timestamp
parameter may contain uninitialized stack memory (e.g., when PHC is
disabled or in blocked state) or invalid hardware values. Passing
these to userspace via the PTP ioctl is both a security issue
(information leak) and a correctness bug.

Fix by checking the return code after releasing the lock and only
setting the output timestamp on success.

Fixes: e0ea34158ee8 ("net: ena: Add PHC support in the ENA driver")
Cc: stable@vger.kernel.org
Signed-off-by: Arthur Kiyanovski <akiyano@amazon.com>
---
 drivers/net/ethernet/amazon/ena/ena_phc.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/amazon/ena/ena_phc.c b/drivers/net/ethernet/amazon/ena/ena_phc.c
index 7867e893fd15..c2a3ff1ef645 100644
--- a/drivers/net/ethernet/amazon/ena/ena_phc.c
+++ b/drivers/net/ethernet/amazon/ena/ena_phc.c
@@ -46,9 +46,12 @@ static int ena_phc_gettimex64(struct ptp_clock_info *clock_info,
 
 	spin_unlock_irqrestore(&phc_info->lock, flags);
 
+	if (rc)
+		return rc;
+
 	*ts = ns_to_timespec64(timestamp_nsec);
 
-	return rc;
+	return 0;
 }
 
 static int ena_phc_settime64(struct ptp_clock_info *clock_info,
-- 
2.47.3