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tracing: Add recursion protection in kernel stack trace recording

PATCH New Leon Chen 1 participant 1 message Feb 28 Stable branch

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PATCH 1/1 tracing: Add recursion protection in kernel stack trace recording

From: Steven Rostedt <[email protected]>

[ Upstream commit 5f1ef0dfcb5b7f4a91a9b0e0ba533efd9f7e2cdb ]

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/[email protected]/ open here
Cc [email protected]
Cc Masami Hiramatsu <[email protected]>
Cc Mathieu Desnoyers <[email protected]>
Cc Joel Fernandes <[email protected]>
Cc "Paul E. McKenney" <[email protected]>
Cc Boqun Feng <[email protected]>
Link https://patch.msgid.link/[email protected] open here
Reported-by Yao Kai <[email protected]>
Tested-by Yao Kai <[email protected]>
Fixes 5f5fa7ea89dc ("rcu: Don't use negative nesting depth in __rcu_read_unlock()")
Signed-off-by Steven Rostedt (Google) <[email protected]>
Signed-off-by Leon Chen <[email protected]>
---
 include/linux/trace_recursion.h | 9 +++++++++
 kernel/trace/trace.c            | 6 ++++++
 2 files changed, 15 insertions(+)
include/linux/trace_recursion.h +9 -0
index d48cd92d2364..67e6a9923d56 100644
@@ -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.

@@ -97,6 +104,8 @@ 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)
 
 /*
kernel/trace/trace.c +6 -0
index a111be83c369..3e0be2baeed1 100644
@@ -3105,6 +3105,11 @@ static void __ftrace_trace_stack(struct trace_buffer *buffer,
 	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()

@@ -3162,6 +3167,7 @@ static void __ftrace_trace_stack(struct trace_buffer *buffer,
 	__this_cpu_dec(ftrace_stack_reserve);
 	preempt_enable_notrace();
 
+	trace_clear_recursion(bit);
 }
 
 static inline void ftrace_trace_stack(struct trace_array *tr,
Signature · 1 line
2.35.3