[PATCH 6.12 117/337] tracing/mmiotrace: Add NULL check for mmio_trace_array in logging functions

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

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

From: Masami Hiramatsu (Google) <[email protected]>

[ Upstream commit 12b80cdbc54cf615b4717a4e8180063408091ea2 ]

mmio_trace_rw() and mmio_trace_mapping() retrieve mmio_trace_array into
tr and pass it to __trace_mmiotrace_rw() and __trace_mmiotrace_map().
If these functions are invoked while mmio_trace_array is NULL (e.g. before
initialization or after disabled), accessing tr->array_buffer.buffer will
result in a NULL pointer dereference crash.

Fix this by adding an explicit NULL check for tr at the beginning of
__trace_mmiotrace_rw() and __trace_mmiotrace_map().

Link: https://patch.msgid.link/178524300062.56416.8362487250709962380.stgit@devnote2
Fixes: f984b51e0779 ("ftrace: add mmiotrace plugin")
Assisted-by: Antigravity:gemini-3.6-flash
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Steven Rostedt <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
 kernel/trace/trace_mmiotrace.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
index 6b964471265e1..251ed7051e409 100644
--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c
@@ -295,11 +295,15 @@ static void __trace_mmiotrace_rw(struct trace_array *tr,
 				struct trace_array_cpu *data,
 				struct mmiotrace_rw *rw)
 {
-	struct trace_buffer *buffer = tr->array_buffer.buffer;
+	struct trace_buffer *buffer;
 	struct ring_buffer_event *event;
 	struct trace_mmiotrace_rw *entry;
 	unsigned int trace_ctx;
 
+	if (!tr)
+		return;
+
+	buffer = tr->array_buffer.buffer;
 	trace_ctx = tracing_gen_ctx_flags(0);
 	event = trace_buffer_lock_reserve(buffer, TRACE_MMIO_RW,
 					  sizeof(*entry), trace_ctx);
@@ -324,11 +328,15 @@ static void __trace_mmiotrace_map(struct trace_array *tr,
 				struct trace_array_cpu *data,
 				struct mmiotrace_map *map)
 {
-	struct trace_buffer *buffer = tr->array_buffer.buffer;
+	struct trace_buffer *buffer;
 	struct ring_buffer_event *event;
 	struct trace_mmiotrace_map *entry;
 	unsigned int trace_ctx;
 
+	if (!tr)
+		return;
+
+	buffer = tr->array_buffer.buffer;
 	trace_ctx = tracing_gen_ctx_flags(0);
 	event = trace_buffer_lock_reserve(buffer, TRACE_MMIO_MAP,
 					  sizeof(*entry), trace_ctx);
-- 
2.53.0