linux-kernel - [PATCH] ftrace: Free the trampoline when ftrace

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Message-Id: <20200831122631.28057-1-mbenes@suse.cz>
Date:   Mon, 31 Aug 2020 14:26:31 +0200
From:   Miroslav Benes <mbenes@...e.cz>
To:     rostedt@...dmis.org, mingo@...hat.com
Cc:     peterz@...radead.org, adrian.hunter@...el.com,
        masami.hiramatsu.pt@...achi.com, linux-kernel@...r.kernel.org,
        Miroslav Benes <mbenes@...e.cz>
Subject: [PATCH] ftrace: Free the trampoline when ftrace_startup() fails

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.

Fixes: fc0ea795f53c ("ftrace: Add symbols for ftrace trampolines")
Signed-off-by: Miroslav Benes <mbenes@...e.cz>
---

It would be fair to add

Fixes: f8b8be8a310a ("ftrace, kprobes: Support IPMODIFY flag to find IP modify conflict")

too. The situation was a bit more complicated back then though since
RCU-tasks support was missing.

 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)
+			ftrace_trampoline_free(ops);
 		return ret;
 	}
 
-- 
2.28.0