[PATCH] tracing: Fix mmiotrace possible NULL dereferencing of hiter->dev

From: Steven Rostedt <rostedt@goodmis.org>

If the mmio_pipe_open() fails to find a PCI device, the hiter->dev
will be assigned to NULL. The mmiotrace read() function dereferences the
hiter->dev if hiter exists.

Change the test of the read to not only check hiter being NULL, but also
the hiter->dev before dereferencing it.

Cc: stable@vger.kernel.org
Fixes: f984b51e0779 ("ftrace: add mmiotrace plugin")
Reported-by: Sashiko
Link: https://sashiko.dev/#/patchset/20260715143604.14481-1-gaikwad.dcg%40gmail.com
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
 kernel/trace/trace_mmiotrace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
index 20812e7f911f..b88b8d9923ad 100644
--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c

@@ -145,7 +145,7 @@ static ssize_t mmio_read(struct trace_iterator *iter, struct file *filp,
 		goto print_out;
 	}
 
-	if (!hiter)
+	if (!hiter || !hiter->dev)
 		return 0;
 
 	mmio_print_pcidev(s, hiter->dev);

-- 
2.53.0