[for-linus][PATCH 3/5] ftrace: Make ftrace_graph_ent depth field signed

[for-linus][PATCH 3/5] ftrace: Make ftrace_graph_ent depth field signed

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

The code has integrity checks to make sure that depth never goes below
zero. But the depth field has recently been converted to unsigned long
from "int" (for alignment reasons). As unsigned long can never be less
than zero, the integrity checks no longer work.

Convert depth to long from unsigned long to allow the integrity checks to
work again.

Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: pengdonglin <pengdonglin@xiaomi.com>
Link: https://patch.msgid.link/20260102143148.251c2e16@gandalf.local.home
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/all/aS6kGi0maWBl-MjZ@stanley.mountain/
Fixes: f83ac7544fbf7 ("function_graph: Enable funcgraph-args and funcgraph-retaddr to work simultaneously")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 include/linux/ftrace.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 770f0dc993cc..a3a8989e3268 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -1167,7 +1167,7 @@ static inline void ftrace_init(void) { }
  */
 struct ftrace_graph_ent {
 	unsigned long func; /* Current function */
-	unsigned long depth;
+	long depth; /* signed to check for less than zero */
 } __packed;
 
 /*
-- 
2.51.0

[for-linus][PATCH 4/5] tracing: Add recursion protection in kernel stack trace recording

[Steven Rostedt]

From: Steven Rostedt <rostedt@goodmis.org>

A bug was reported about an infinite recursion caused by tracing the rcu
events with the kernel stack trace trigger enabled. The stack trace code
called back into RCU which then called the stack trace again.

Expand the ftrace recursion protection to add a set of bits to protect
events from recursion. Each bit represents the context that the event is
in (normal, softirq, interrupt and NMI).

Have the stack trace code use the interrupt context to protect against
recursion.

Note, the bug showed an issue in both the RCU code as well as the tracing
stacktrace code. This only handles the tracing stack trace side of the
bug. The RCU fix will be handled separately.

Link: https://lore.kernel.org/all/20260102122807.7025fc87@gandalf.local.home/

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20260105203141.515cd49f@gandalf.local.home
Reported-by: Yao Kai <yaokai34@huawei.com>
Tested-by: Yao Kai <yaokai34@huawei.com>
Fixes: 5f5fa7ea89dc ("rcu: Don't use negative nesting depth in __rcu_read_unlock()")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 include/linux/trace_recursion.h | 9 +++++++++
 kernel/trace/trace.c            | 6 ++++++
 2 files changed, 15 insertions(+)

diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
index ae04054a1be3..e6ca052b2a85 100644
--- a/include/linux/trace_recursion.h
+++ b/include/linux/trace_recursion.h
@@ -34,6 +34,13 @@ enum {
 	TRACE_INTERNAL_SIRQ_BIT,
 	TRACE_INTERNAL_TRANSITION_BIT,
 
+	/* Internal event use recursion bits */
+	TRACE_INTERNAL_EVENT_BIT,
+	TRACE_INTERNAL_EVENT_NMI_BIT,
+	TRACE_INTERNAL_EVENT_IRQ_BIT,
+	TRACE_INTERNAL_EVENT_SIRQ_BIT,
+	TRACE_INTERNAL_EVENT_TRANSITION_BIT,
+
 	TRACE_BRANCH_BIT,
 /*
  * Abuse of the trace_recursion.
@@ -58,6 +65,8 @@ enum {
 
 #define TRACE_LIST_START	TRACE_INTERNAL_BIT
 
+#define TRACE_EVENT_START	TRACE_INTERNAL_EVENT_BIT
+
 #define TRACE_CONTEXT_MASK	((1 << (TRACE_LIST_START + TRACE_CONTEXT_BITS)) - 1)
 
 /*
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6f2148df14d9..aef9058537d5 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3012,6 +3012,11 @@ static void __ftrace_trace_stack(struct trace_array *tr,
 	struct ftrace_stack *fstack;
 	struct stack_entry *entry;
 	int stackidx;
+	int bit;
+
+	bit = trace_test_and_set_recursion(_THIS_IP_, _RET_IP_, TRACE_EVENT_START);
+	if (bit < 0)
+		return;
 
 	/*
 	 * Add one, for this function and the call to save_stack_trace()
@@ -3080,6 +3085,7 @@ static void __ftrace_trace_stack(struct trace_array *tr,
 	/* Again, don't let gcc optimize things here */
 	barrier();
 	__this_cpu_dec(ftrace_stack_reserve);
+	trace_clear_recursion(bit);
 }
 
 static inline void ftrace_trace_stack(struct trace_array *tr,
-- 
2.51.0