From: Steven Rostedt <rostedt@goodmis.org> mainline inclusion from mainline-v6.19-rc5 commit 5f1ef0dfcb5b7f4a91a9b0e0ba533efd9f7e2cdb category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/8496 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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> Conflicts: kernel/trace/trace.c kernel/trace/trace.h include/linux/trace_recursion.h [The conflicts are due to we did not backport 0264c8c9e1b5 ("ftrace: Move the recursion testing into global headers"), which is a cleanup patch] Signed-off-by: Tengda Wu <wutengda@huaweicloud.com> --- kernel/trace/trace.c | 6 ++++++ kernel/trace/trace.h | 9 +++++++++ 2 files changed, 15 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 6c5a503987e7..50dda48f6e6b 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2994,6 +2994,11 @@ 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(TRACE_EVENT_START); + if (bit < 0) + return; /* * Add one, for this function and the call to save_stack_trace() @@ -3049,6 +3054,7 @@ static void __ftrace_trace_stack(struct trace_buffer *buffer, /* Again, don't let gcc optimize things here */ barrier(); __this_cpu_dec(ftrace_stack_reserve); + trace_clear_recursion(bit); preempt_enable_notrace(); } diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index 139d4e47489d..27e9d7659a48 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -599,6 +599,13 @@ 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. @@ -659,6 +666,8 @@ 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) enum { -- 2.34.1