[PATCH v5 01/17] i3c: renesas: Check that the transfer is valid before accessing it

[Claudiu Beznea]

From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>

The Renesas I3C driver uses an asynchronous model to transfer data. It
prepares a struct renesas_i3c_xfer, enqueues it, and waits for completion.
The interrupt handler dequeues the transfer, updates/uses it, and signals
the waiting thread.

If the completion times out, the waiting thread dequeues the transfer and
free it. If an interrupt fires after that, the handler may access freed
memory, leading to crashes.

Check that the transfer is still valid before accessing it in the
interrupt handler. With it clear any status flags and disable all
the interrupts to avoid triggering the same interrupts again.

Fixes: d028219a9f14 ("i3c: master: Add basic driver for the Renesas I3C controller")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
---

Changes in v5:
- introduced renesas_i3c_irqs_mask_and_clear_locked() that keeps
  unified the IRQ mask and clean path
- updated the patch description

Changes in v4:
- disable also the interrupts
- dropped the Rb tag

Changes in v3:
- none

Changes in v2:
- clean the IRQ status bits before returning IRQ_HANDLED and adjusted the
  patch description to reflect this change
- collected Frank's tag. Frank, please let me know if you consider
  I should drop your tag. Thanks!

 drivers/i3c/master/renesas-i3c.c | 52 +++++++++++++++++++++++++++-----
 1 file changed, 45 insertions(+), 7 deletions(-)

diff --git a/drivers/i3c/master/renesas-i3c.c b/drivers/i3c/master/renesas-i3c.c
index f39c449922ca..38b8428f464c 100644
--- a/drivers/i3c/master/renesas-i3c.c
+++ b/drivers/i3c/master/renesas-i3c.c
@@ -433,6 +433,21 @@ static void renesas_i3c_enqueue_xfer(struct renesas_i3c *i3c, struct renesas_i3c
 	}
 }
 
+static void renesas_i3c_irqs_mask_and_clear_locked(struct renesas_i3c *i3c)
+{
+	/* Disable all the interrupts. */
+	renesas_writel(i3c->regs, BIE, 0);
+	renesas_writel(i3c->regs, NTIE, 0);
+
+	/* Clear normal transfer status flags. */
+	renesas_writel(i3c->regs, NTST, 0);
+
+	/* Clear bus status flags. */
+	renesas_writel(i3c->regs, BST, 0);
+	/* Read back registers to confirm writes have fully propagated. */
+	renesas_readl(i3c->regs, BST);
+}
+
 static void renesas_i3c_wait_xfer(struct renesas_i3c *i3c, struct renesas_i3c_xfer *xfer)
 {
 	unsigned long time_left;
@@ -1014,6 +1029,11 @@ static irqreturn_t renesas_i3c_tx_isr(int irq, void *data)
 
 	scoped_guard(spinlock, &i3c->xferqueue.lock) {
 		xfer = i3c->xferqueue.cur;
+		if (!xfer) {
+			renesas_i3c_irqs_mask_and_clear_locked(i3c);
+			return IRQ_HANDLED;
+		}
+
 		cmd = xfer->cmds;
 
 		if (xfer->is_i2c_xfer) {
@@ -1054,6 +1074,11 @@ static irqreturn_t renesas_i3c_resp_isr(int irq, void *data)
 
 	scoped_guard(spinlock, &i3c->xferqueue.lock) {
 		xfer = i3c->xferqueue.cur;
+		if (!xfer) {
+			renesas_i3c_irqs_mask_and_clear_locked(i3c);
+			return IRQ_HANDLED;
+		}
+
 		cmd = xfer->cmds;
 
 		/* Clear the Respone Queue Full status flag*/
@@ -1138,6 +1163,11 @@ static irqreturn_t renesas_i3c_tend_isr(int irq, void *data)
 
 	scoped_guard(spinlock, &i3c->xferqueue.lock) {
 		xfer = i3c->xferqueue.cur;
+		if (!xfer) {
+			renesas_i3c_irqs_mask_and_clear_locked(i3c);
+			return IRQ_HANDLED;
+		}
+
 		cmd = xfer->cmds;
 
 		if (xfer->is_i2c_xfer) {
@@ -1184,6 +1214,11 @@ static irqreturn_t renesas_i3c_rx_isr(int irq, void *data)
 
 	scoped_guard(spinlock, &i3c->xferqueue.lock) {
 		xfer = i3c->xferqueue.cur;
+		if (!xfer) {
+			renesas_i3c_irqs_mask_and_clear_locked(i3c);
+			return IRQ_HANDLED;
+		}
+
 		cmd = xfer->cmds;
 
 		if (xfer->is_i2c_xfer) {
@@ -1234,15 +1269,13 @@ static irqreturn_t renesas_i3c_stop_isr(int irq, void *data)
 	struct renesas_i3c_xfer *xfer;
 
 	scoped_guard(spinlock, &i3c->xferqueue.lock) {
-		xfer = i3c->xferqueue.cur;
-
-		/* read back registers to confirm writes have fully propagated */
-		renesas_writel(i3c->regs, BST, 0);
-		renesas_readl(i3c->regs, BST);
-		renesas_writel(i3c->regs, BIE, 0);
-		renesas_clear_bit(i3c->regs, NTST, NTST_TDBEF0 | NTST_RDBFF0);
+		renesas_i3c_irqs_mask_and_clear_locked(i3c);
 		renesas_clear_bit(i3c->regs, SCSTRCTL, SCSTRCTL_RWE);
 
+		xfer = i3c->xferqueue.cur;
+		if (!xfer)
+			return IRQ_HANDLED;
+
 		xfer->ret = 0;
 		complete(&xfer->comp);
 	}
@@ -1259,6 +1292,11 @@ static irqreturn_t renesas_i3c_start_isr(int irq, void *data)
 
 	scoped_guard(spinlock, &i3c->xferqueue.lock) {
 		xfer = i3c->xferqueue.cur;
+		if (!xfer) {
+			renesas_i3c_irqs_mask_and_clear_locked(i3c);
+			return IRQ_HANDLED;
+		}
+
 		cmd = xfer->cmds;
 
 		if (xfer->is_i2c_xfer) {
-- 
2.43.0