[PATCH 6.18 170/175] spi: tegra210-quad: Protect curr_xfer check in IRQ handler

Greg Kroah-Hartman
2026-02-09T14:34:32Z

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 7fe16ed7e84bd..83def82fe48c1 100644
--- a/drivers/spi/spi-tegra210-quad.c
+++ b/drivers/spi/spi-tegra210-quad.c
@@ -1393,6 +1393,11 @@ 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);
@@ -1463,6 +1468,11 @@ 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 (num_errors) {
tegra_qspi_dma_unmap_xfer(tqspi, t);
tegra_qspi_handle_error(tqspi);
@@ -1501,6 +1511,7 @@ 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;

/*
@@ -1518,7 +1529,9 @@ 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;
@@ -1535,7 +1548,14 @@ 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);

--
2.51.0