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

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Message-ID: <alpine.LSU.2.21.2008311455440.16475@pobox.suse.cz>
Date:   Mon, 31 Aug 2020 14:56:57 +0200 (CEST)
From:   Miroslav Benes <mbenes@...e.cz>
To:     rostedt@...dmis.org, mingo@...hat.com
cc:     peterz@...radead.org, adrian.hunter@...el.com,
        linux-kernel@...r.kernel.org, mhiramat@...nel.org
Subject: Re: [PATCH] ftrace: Free the trampoline when ftrace_startup()
 fails

I used Masami's address which did not work. Sorry about that. Should be ok 
now.

On Mon, 31 Aug 2020, Miroslav Benes wrote:

> 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
>