[PATCH 10/33] scsi: qla2xxx: Fix FCE trace use-after-free during firmware dump

qla2x00_free_fce_trace() freed and cleared ha->fce while holding only
fce_mutex. The firmware-dump consumers qla27xx_fwdt_entry_t264() and
qla25xx_copy_fce() read ha->fce (NULL check followed by a copy of the
buffer) under hardware_lock and never take fce_mutex. A debugfs FCE
disable could therefore free the DMA buffer between a dump's NULL check
and its copy, resulting in a use-after-free.

Unpublish ha->fce under hardware_lock, then release the lock and free
the DMA buffer (dma_free_coherent() may sleep). A concurrent dump either
completes its check and copy with the buffer still valid, or observes
ha->fce == NULL and skips it.

Fixes: 841df27d619e ("scsi: qla2xxx: Move FCE Trace buffer allocation to user control")
Cc: [email protected]
Reported-by: Sashiko <[email protected]>
Signed-off-by: Nilesh Javali <[email protected]>
---
 drivers/scsi/qla2xxx/qla_init.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/qla2xxx/qla_init.c b/drivers/scsi/qla2xxx/qla_init.c
index fb417364fa75..fed6dbc3b6ae 100644
--- a/drivers/scsi/qla2xxx/qla_init.c
+++ b/drivers/scsi/qla2xxx/qla_init.c
@@ -3752,11 +3752,27 @@ int qla2x00_alloc_fce_trace(scsi_qla_host_t *vha)
 
 void qla2x00_free_fce_trace(struct qla_hw_data *ha)
 {
-	if (!ha->fce)
+	void *fce;
+	dma_addr_t fce_dma;
+	unsigned long flags;
+
+	/*
+	 * Unpublish ha->fce under hardware_lock so a firmware dump in
+	 * progress (which reads ha->fce under the same lock) cannot race
+	 * with the buffer being freed.
+	 */
+	spin_lock_irqsave(&ha->hardware_lock, flags);
+	if (!ha->fce) {
+		spin_unlock_irqrestore(&ha->hardware_lock, flags);
 		return;
-	dma_free_coherent(&ha->pdev->dev, FCE_SIZE, ha->fce, ha->fce_dma);
+	}
+	fce = ha->fce;
+	fce_dma = ha->fce_dma;
 	ha->fce = NULL;
 	ha->fce_dma = 0;
+	spin_unlock_irqrestore(&ha->hardware_lock, flags);
+
+	dma_free_coherent(&ha->pdev->dev, FCE_SIZE, fce, fce_dma);
 }
 
 static void
-- 
2.47.3