[PATCH v2] dmaengine: fsl-edma: tracing: no ptr dereference during log output

The fsl edma events store a pointer to a struct fsl_edma_engine in the
ringbuffer and dereference it when a log entry is printed. At this time,
the pointer may no longer be valid.

Event injection can be used to trigger a crash:

$ cd /sys/kernel/tracing
$ echo 'value = 0' > events/fsl_edma/edma_writeb/inject
$ cat trace

The log output needs only edma->membase. Add a membase field at the end
of the event and use the new field for log output. Keep the existing
fields for backward compatibility.

Fixes: 11102d0c343b ("dmaengine: fsl-edma: add trace event support")
Cc: [email protected]
Reviewed-by: Steven Rostedt <[email protected]>
Signed-off-by: Martin Kaiser <[email protected]>
---
v2:
 - dmaengine prefix in the subject line
 - Cc stable
 - Steven's Reviewed tag

 drivers/dma/fsl-edma-trace.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/fsl-edma-trace.h b/drivers/dma/fsl-edma-trace.h
index d3541301a247..45d964a3726d 100644
--- a/drivers/dma/fsl-edma-trace.h
+++ b/drivers/dma/fsl-edma-trace.h
@@ -19,14 +19,16 @@ DECLARE_EVENT_CLASS(edma_log_io,
 		__field(struct fsl_edma_engine *, edma)
 		__field(void __iomem *, addr)
 		__field(u32, value)
+		__field(void __iomem *, membase)
 	),
 	TP_fast_assign(
 		__entry->edma = edma;
 		__entry->addr = addr;
 		__entry->value = value;
+		__entry->membase = edma->membase;
 	),
 	TP_printk("offset %08x: value %08x",
-		(u32)(__entry->addr - __entry->edma->membase), __entry->value)
+		(u32)(__entry->addr - __entry->membase), __entry->value)
 );
 
 DEFINE_EVENT(edma_log_io, edma_readl,
-- 
2.43.7