From: Miroslav Benes <mbenes@suse.cz>
Date: Mon, 31 Aug 2020 14:26:31 +0200
Subject: ftrace: Free the trampoline when ftrace_startup() fails
Git-commit: d5e47505e02666d5b3fe99212e0100791847dc8d
Patch-mainline: v5.9-rc7
References: git-fixes

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@suse.cz

Fixes: fc0ea795f53c ("ftrace: Add symbols for ftrace trampolines")
Fixes: f8b8be8a310a ("ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict")
[
  mb: backport modification, we need to only remove the trampoline. Commit
  fc0ea795f53c is not backported.
]
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 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)
 		__unregister_ftrace_function(ops);
 		ftrace_start_up--;
 		ops->flags &= ~FTRACE_OPS_FL_ENABLED;
+		if (ops->flags & FTRACE_OPS_FL_DYNAMIC)
+			arch_ftrace_trampoline_free(ops);
 		return ret;
 	}