Re: [PATCH bpf] ftrace: Add missing ftrace_lock to update_ftrace_direct_add/del

[Steven Rostedt]

On Mon,  2 Mar 2026 09:16:22 +0100
Jiri Olsa <jolsa@xxxxxxxxxx> wrote:

> Ihor and Kumar reported splat from ftrace_get_addr_curr [1], which happened
> because of the missing ftrace_lock in update_ftrace_direct_add/del functions
> allowing concurrent access to ftrace internals.
> 
> The ftrace_update_ops function must be guarded by ftrace_lock, adding that.
> 
> Fixes: 05dc5e9c1fe1 ("ftrace: Add update_ftrace_direct_add function")
> Fixes: 8d2c1233f371 ("ftrace: Add update_ftrace_direct_del function")
> Reported-by: Ihor Solodrai <ihor.solodrai@xxxxxxxxx>
> Reported-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> Closes: https://lore.kernel.org/bpf/1b58ffb2-92ae-433a-ba46-95294d6edea2@xxxxxxxxx/
> Tested-by: Ihor Solodrai <ihor.solodrai@xxxxxxxxx>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>

Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>

-- Steve

> ---
>  kernel/trace/ftrace.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 827fb9a0bf0d..8baf61c9be6d 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -6404,6 +6404,7 @@ int update_ftrace_direct_add(struct ftrace_ops *ops, struct ftrace_hash *hash)
>  			new_filter_hash = old_filter_hash;
>  		}
>  	} else {
> +		guard(mutex)(&ftrace_lock);
>  		err = ftrace_update_ops(ops, new_filter_hash, EMPTY_HASH);
>  		/*
>  		 * new_filter_hash is dup-ed, so we need to release it anyway,
> @@ -6530,6 +6531,7 @@ int update_ftrace_direct_del(struct ftrace_ops *ops, struct ftrace_hash *hash)
>  			ops->func_hash->filter_hash = NULL;
>  		}
>  	} else {
> +		guard(mutex)(&ftrace_lock);
>  		err = ftrace_update_ops(ops, new_filter_hash, EMPTY_HASH);
>  		/*
>  		 * new_filter_hash is dup-ed, so we need to release it anyway,