[PATCH 6.1 238/609] tracing: Fix mmiotrace possible NULL dereferencing of hiter->dev

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Steven Rostedt <[email protected]>

commit 144f29e85702234b23d2a62abf723e6a17eb5427 upstream.

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: [email protected]
Link: https://patch.msgid.link/[email protected]
Fixes: f984b51e0779 ("ftrace: add mmiotrace plugin")
Reported-by: Sashiko <[email protected]>
Link: https://sashiko.dev/#/patchset/20260715143604.14481-1-gaikwad.dcg%40gmail.com
Signed-off-by: Steven Rostedt <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 kernel/trace/trace_mmiotrace.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c
@@ -146,7 +146,7 @@ static ssize_t mmio_read(struct trace_it
 		goto print_out;
 	}
 
-	if (!hiter)
+	if (!hiter || !hiter->dev)
 		return 0;
 
 	mmio_print_pcidev(s, hiter->dev);