[PATCH 02/13] net/ena/base: fix race in PHC destroy

[Shai Brandes <shaibran@amazon.com>]

ena_com_phc_get_timestamp() checked phc->active and cached the
resp pointer from ena_dev->phc.virt_addr before acquiring the PHC
spinlock, so neither the liveness check nor the pointer read was
serialised against teardown.

If ena_com_phc_destroy() runs in that window it clears active,
releases the lock, frees the PHC DMA memory and sets virt_addr to
NULL. The reader then dereferences either a pointer to already
freed memory or a NULL virt_addr, depending on where it was
preempted, crashing the application on PHC teardown or device
reconfiguration.

Move the phc->active check and the resp pointer assignment inside
the spinlock so that destroy cannot free the DMA memory while a
timestamp read is in progress.

Fixes: f73f53f7dc7a ("net/ena: upgrade HAL")
Cc: stable@dpdk.org

Signed-off-by: Shai Brandes <shaibran@amazon.com>
---
 drivers/net/ena/base/ena_com.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ena/base/ena_com.c b/drivers/net/ena/base/ena_com.c
index fd59fc407b..f5b3cd70c8 100644
--- a/drivers/net/ena/base/ena_com.c
+++ b/drivers/net/ena/base/ena_com.c
@@ -1996,20 +1996,23 @@ void ena_com_phc_destroy(struct ena_com_dev *ena_dev)
 
 int ena_com_phc_get_timestamp(struct ena_com_dev *ena_dev, u64 *timestamp)
 {
-	volatile struct ena_admin_phc_resp *resp = ena_dev->phc.virt_addr;
 	const ena_time_high_res_t zero_system_time = ENA_TIME_INIT_HIGH_RES();
 	struct ena_com_phc_info *phc = &ena_dev->phc;
+	volatile struct ena_admin_phc_resp *resp;
 	ena_time_high_res_t expire_time;
 	ena_time_high_res_t block_time;
 	unsigned long flags = 0;
 	int ret = ENA_COM_OK;
 
+	ENA_SPINLOCK_LOCK(phc->lock, flags);
+
 	if (!phc->active) {
+		ENA_SPINLOCK_UNLOCK(phc->lock, flags);
 		ena_trc_err(ena_dev, "PHC feature is not active in the device\n");
 		return ENA_COM_UNSUPPORTED;
 	}
 
-	ENA_SPINLOCK_LOCK(phc->lock, flags);
+	resp = ena_dev->phc.virt_addr;
 
 	/* Check if PHC is in blocked state */
 	if (unlikely(ENA_TIME_COMPARE_HIGH_RES(phc->system_time, zero_system_time))) {
-- 
2.17.1