[PATCH 6.12.y] spi: tegra210-quad: Protect curr_xfer check in IRQ handler

[PATCH 6.12.y] spi: tegra210-quad: Protect curr_xfer check in IRQ handler

[Jianqiang kang]

From: Breno Leitao <leitao@debian.org>

[ Upstream commit edf9088b6e1d6d88982db7eb5e736a0e4fbcc09e ]

Now that all other accesses to curr_xfer are done under the lock,
protect the curr_xfer NULL check in tegra_qspi_isr_thread() with the
spinlock. Without this protection, the following race can occur:

  CPU0 (ISR thread)              CPU1 (timeout path)
  ----------------               -------------------
  if (!tqspi->curr_xfer)
    // sees non-NULL
                                 spin_lock()
                                 tqspi->curr_xfer = NULL
                                 spin_unlock()
  handle_*_xfer()
    spin_lock()
    t = tqspi->curr_xfer  // NULL!
    ... t->len ...        // NULL dereference!

With this patch, all curr_xfer accesses are now properly synchronized.

Although all accesses to curr_xfer are done under the lock, in
tegra_qspi_isr_thread() it checks for NULL, releases the lock and
reacquires it later in handle_cpu_based_xfer()/handle_dma_based_xfer().
There is a potential for an update in between, which could cause a NULL
pointer dereference.

To handle this, add a NULL check inside the handlers after acquiring
the lock. This ensures that if the timeout path has already cleared
curr_xfer, the handler will safely return without dereferencing the
NULL pointer.

Fixes: b4e002d8a7ce ("spi: tegra210-quad: Fix timeout handling")
Signed-off-by: Breno Leitao <leitao@debian.org>
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://patch.msgid.link/20260126-tegra_xfer-v2-6-6d2115e4f387@debian.org
Signed-off-by: Mark Brown <broonie@kernel.org>
[ Minor conflict resolved. ]
Signed-off-by: Jianqiang kang <jianqkang@sina.cn>
---
 drivers/spi/spi-tegra210-quad.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/spi/spi-tegra210-quad.c b/drivers/spi/spi-tegra210-quad.c
index edc9d400728a..14dd98b92bd9 100644
--- a/drivers/spi/spi-tegra210-quad.c
+++ b/drivers/spi/spi-tegra210-quad.c
@@ -1351,6 +1351,11 @@ static irqreturn_t handle_cpu_based_xfer(struct tegra_qspi *tqspi)
 	spin_lock_irqsave(&tqspi->lock, flags);
 	t = tqspi->curr_xfer;
 
+	if (!t) {
+		spin_unlock_irqrestore(&tqspi->lock, flags);
+		return IRQ_HANDLED;
+	}
+
 	if (tqspi->tx_status ||  tqspi->rx_status) {
 		tegra_qspi_handle_error(tqspi);
 		complete(&tqspi->xfer_completion);
@@ -1419,6 +1424,11 @@ static irqreturn_t handle_dma_based_xfer(struct tegra_qspi *tqspi)
 	spin_lock_irqsave(&tqspi->lock, flags);
 	t = tqspi->curr_xfer;
 
+	if (!t) {
+		spin_unlock_irqrestore(&tqspi->lock, flags);
+		return IRQ_HANDLED;
+	}
+
 	if (err) {
 		tegra_qspi_dma_unmap_xfer(tqspi, t);
 		tegra_qspi_handle_error(tqspi);
@@ -1457,6 +1467,7 @@ static irqreturn_t handle_dma_based_xfer(struct tegra_qspi *tqspi)
 static irqreturn_t tegra_qspi_isr_thread(int irq, void *context_data)
 {
 	struct tegra_qspi *tqspi = context_data;
+	unsigned long flags;
 	u32 status;
 
 	/*
@@ -1474,7 +1485,9 @@ static irqreturn_t tegra_qspi_isr_thread(int irq, void *context_data)
 	 * If no transfer is in progress, check if this was a real interrupt
 	 * that the timeout handler already processed, or a spurious one.
 	 */
+	spin_lock_irqsave(&tqspi->lock, flags);
 	if (!tqspi->curr_xfer) {
+		spin_unlock_irqrestore(&tqspi->lock, flags);
 		/* Spurious interrupt - transfer not ready */
 		if (!(status & QSPI_RDY))
 			return IRQ_NONE;
@@ -1491,7 +1504,14 @@ static irqreturn_t tegra_qspi_isr_thread(int irq, void *context_data)
 		tqspi->rx_status = tqspi->status_reg & (QSPI_RX_FIFO_OVF | QSPI_RX_FIFO_UNF);
 
 	tegra_qspi_mask_clear_irq(tqspi);
+	spin_unlock_irqrestore(&tqspi->lock, flags);
 
+	/*
+	 * Lock is released here but handlers safely re-check curr_xfer under
+	 * lock before dereferencing.
+	 * DMA handler also needs to sleep in wait_for_completion_*(), which
+	 * cannot be done while holding spinlock.
+	 */
 	if (!tqspi->is_curr_dma_xfer)
 		return handle_cpu_based_xfer(tqspi);
 
-- 
2.34.1

Re: [PATCH 6.12.y] spi: tegra210-quad: Protect curr_xfer check in IRQ handler

[Breno Leitao]

On Tue, Mar 24, 2026 at 02:08:32PM +0800, Jianqiang kang wrote:
> From: Breno Leitao <leitao@debian.org>
> 
> [ Upstream commit edf9088b6e1d6d88982db7eb5e736a0e4fbcc09e ]
> 
> Now that all other accesses to curr_xfer are done under the lock,
> protect the curr_xfer NULL check in tegra_qspi_isr_thread() with the
> spinlock. Without this protection, the following race can occur:
> 
>   CPU0 (ISR thread)              CPU1 (timeout path)
>   ----------------               -------------------
>   if (!tqspi->curr_xfer)
>     // sees non-NULL
>                                  spin_lock()
>                                  tqspi->curr_xfer = NULL
>                                  spin_unlock()
>   handle_*_xfer()
>     spin_lock()
>     t = tqspi->curr_xfer  // NULL!
>     ... t->len ...        // NULL dereference!
> 
> With this patch, all curr_xfer accesses are now properly synchronized.
> 
> Although all accesses to curr_xfer are done under the lock, in
> tegra_qspi_isr_thread() it checks for NULL, releases the lock and
> reacquires it later in handle_cpu_based_xfer()/handle_dma_based_xfer().
> There is a potential for an update in between, which could cause a NULL
> pointer dereference.
> 
> To handle this, add a NULL check inside the handlers after acquiring
> the lock. This ensures that if the timeout path has already cleared
> curr_xfer, the handler will safely return without dereferencing the
> NULL pointer.
> 
> Fixes: b4e002d8a7ce ("spi: tegra210-quad: Fix timeout handling")
> Signed-off-by: Breno Leitao <leitao@debian.org>
> Tested-by: Jon Hunter <jonathanh@nvidia.com>
> Acked-by: Jon Hunter <jonathanh@nvidia.com>
> Acked-by: Thierry Reding <treding@nvidia.com>
> Link: https://patch.msgid.link/20260126-tegra_xfer-v2-6-6d2115e4f387@debian.org
> Signed-off-by: Mark Brown <broonie@kernel.org>
> [ Minor conflict resolved. ]
> Signed-off-by: Jianqiang kang <jianqkang@sina.cn>

Acked-by: Breno Leitao <leitao@debian.org>