[PATCH v4] ata: libahci: delete the SW activity blink timer on port stop

[Hyunjung Ko <hj351016@gmail.com>]

The software activity LED support arms a per-EM-port timer (emp->timer,
ahci_sw_activity_blink) from ahci_sw_activity() on I/O, and the timer
callback re-arms itself while the LED is blinking. The timer lives in
struct ahci_em_priv inside the port's ahci_port_priv, which is allocated
with devm_kzalloc() and freed when the port is torn down.

ahci_port_stop() never deletes this timer - nothing in libahci does - so
when the SW activity LED is in use and the AHCI port is stopped (driver
unbind / module unload) while the blink timer is still pending,
ahci_sw_activity_blink() runs after ahci_port_priv has been freed and
dereferences the freed ahci_em_priv (use-after-free).

Shut the timers down in ahci_port_stop() before the port private data is
released. Iterate every em_priv slot and skip the ones that
ahci_init_sw_activity() never set up (emp->timer.function is NULL), so a
timer armed on a fan-out link whose port multiplier was detached before
port stop is not missed. Because the callback re-arms itself, use
timer_shutdown_sync() so a concurrent re-arm cannot resurrect it.

Not tested on real hardware (needs an AHCI controller with SGPIO
enclosure management and the software activity LED enabled).

Fixes: 18f7ba4c2f4b ("libata/ahci: enclosure management support")
Cc: stable@vger.kernel.org
Signed-off-by: Hyunjung Ko <hj351016@gmail.com>
---
Changes in v4:
- Iterate all pp->em_priv[] slots instead of the current links, so a blink
  timer armed on a fan-out link whose PMP was detached before port stop
  (e.g. by sata_pmp_detach() on failed EH recovery) is still shut down
  (Sashiko AI review). This drops the now-redundant ATA_FLAG_SW_ACTIVITY
  gate, since the emp->timer.function check already skips unset-up slots.
- Correct the Fixes tag to the commit that introduced emp->timer
  (Sashiko AI review).

Changes in v3:
- Shorten the code comment (Niklas Cassel).

Changes in v2:
- Gate the shutdown loop and skip em_priv slots whose timer was never set
  up (Sashiko AI review); superseded by the all-slots iteration in v4.

v3: https://lore.kernel.org/linux-ide/20261110090303.2415681-1-hj351016@gmail.com/

 drivers/ata/libahci.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index 001a6f5..6d73c7f 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -2605,8 +2605,23 @@ static void ahci_port_stop(struct ata_port *ap)
 {
 	const char *emsg = NULL;
 	struct ahci_host_priv *hpriv = ap->host->private_data;
+	struct ahci_port_priv *pp = ap->private_data;
 	void __iomem *host_mmio = hpriv->mmio;
+	struct ahci_em_priv *emp;
 	int rc;
+	int i;
+
+	/*
+	 * Stop the SW activity blink timers before devres frees pp, skipping
+	 * the slots that ahci_init_sw_activity() never set up.  Iterate all
+	 * em_priv slots rather than the current links, so a timer armed on a
+	 * fan-out link whose PMP was detached before port stop is not missed.
+	 */
+	for (i = 0; i < EM_MAX_SLOTS; i++) {
+		emp = &pp->em_priv[i];
+		if (emp->timer.function)
+			timer_shutdown_sync(&emp->timer);
+	}

 	/* de-initialize port */
 	rc = ahci_deinit_port(ap, &emsg);
--
2.43.0