From df45a55788286c541449d82ee09fef3ac5ff77a1 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Tue, 15 Feb 2022 19:31:23 +0100 Subject: [PATCH] powerpc/ftrace: Add recursion protection in prepare_ftrace_return() The function_graph_enter() does not provide any recursion protection. Add a protection in prepare_ftrace_return() in case function_graph_enter() calls something that gets function graph traced. Fixes: 830213786c49 ("powerpc/ftrace: directly call of function graph tracer by ftrace caller") Reported-by: Naveen N. Rao Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/74edf2ff0a60e66b0d9225a137100a86a0557032.1644949750.git.christophe.leroy@csgroup.eu --- arch/powerpc/kernel/trace/ftrace.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c index 74a176e394ef..f21b8fbd418e 100644 --- a/arch/powerpc/kernel/trace/ftrace.c +++ b/arch/powerpc/kernel/trace/ftrace.c @@ -944,6 +944,7 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip, unsigned long sp) { unsigned long return_hooker; + int bit; if (unlikely(ftrace_graph_is_dead())) goto out; @@ -951,10 +952,16 @@ unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip, if (unlikely(atomic_read(¤t->tracing_graph_pause))) goto out; + bit = ftrace_test_recursion_trylock(ip, parent); + if (bit < 0) + goto out; + return_hooker = ppc_function_entry(return_to_handler); if (!function_graph_enter(parent, ip, 0, (unsigned long *)sp)) parent = return_hooker; + + ftrace_test_recursion_unlock(bit); out: return parent; }