[for-linus][PATCH 2/8] ftrace: Free the trampoline when ftrace_startup() fails

From: Steven Rostedt
Date: Mon Sep 21 2020 - 20:27:09 EST

From: Miroslav Benes <mbenes@xxxxxxx>

Commit fc0ea795f53c ("ftrace: Add symbols for ftrace trampolines")
missed to remove ops from new ftrace_ops_trampoline_list in
ftrace_startup() if ftrace_hash_ipmodify_enable() fails there. It may
lead to BUG if such ops come from a module which may be removed.

Moreover, the trampoline itself is not freed in this case.

Fix it by calling ftrace_trampoline_free() during the rollback.

Link: https://lkml.kernel.org/r/20200831122631.28057-1-mbenes@xxxxxxx

Fixes: fc0ea795f53c ("ftrace: Add symbols for ftrace trampolines")
Fixes: f8b8be8a310a ("ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict")
Signed-off-by: Miroslav Benes <mbenes@xxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
kernel/trace/ftrace.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 275441254bb5..656d7cb5a78c 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2862,6 +2862,8 @@ int ftrace_startup(struct ftrace_ops *ops, int command)
ops->flags &= ~FTRACE_OPS_FL_ENABLED;
+ if (ops->flags & FTRACE_OPS_FL_DYNAMIC)
+ ftrace_trampoline_free(ops);
return ret;