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Date:   Mon, 17 Jun 2019 19:18:13 -0400
From:   Steven Rostedt <rostedt@goodmis.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Jessica Yu <jeyu@kernel.org>, linux-kernel@vger.kernel.org,
        jpoimboe@redhat.com, jikos@kernel.org, mbenes@suse.cz,
        pmladek@suse.com, ast@kernel.org, daniel@iogearbox.net
Subject: Re: [RFC][PATCH] module: Propagate MODULE_STATE_COMING notifier
 errors
Message-ID: <20190617191813.2eb37be8@gandalf.local.home>
In-Reply-To: <20190617090335.GX3436@hirez.programming.kicks-ass.net>
References: <20190617090335.GX3436@hirez.programming.kicks-ass.net>
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On Mon, 17 Jun 2019 11:03:35 +0200
Peter Zijlstra <peterz@infradead.org> wrote:

> Some module notifiers; such as jump_label_module_notifier(),
> tracepoint_module_notify(); can fail the MODULE_STATE_COMING callback
> (due to -ENOMEM for example). However module.c:prepare_coming_module()
> ignores all such errors, even though this function can already fail due
> to klp_module_coming().
> 
> Therefore, propagate the notifier error and ensure we call the GOING
> notifier when we do fail, to ensure cleanup for all notifiers that
> didn't fail. Auditing all notifiers to make sure calling GOING without
> COMING first is OK found no obvious problems with that, but it did find
> a whole bunch of issues with return values, so clean those up too.
> 
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Cc: Jiri Kosina <jikos@kernel.org>

I think this patch should get a reviewed by from Josh or Jiri just to
take a look at the change in error paths wrt klp_module_coming() and
klp_module_going() updates.

But other than that.

Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

-- Steve


> Cc: Miroslav Benes <mbenes@suse.cz>
> Cc: Petr Mladek <pmladek@suse.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Alexei Starovoitov <ast@kernel.org>
> Cc: Daniel Borkmann <daniel@iogearbox.net>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
>  drivers/oprofile/buffer_sync.c | 4 ++--
>  kernel/module.c                | 9 +++++----
>  kernel/trace/bpf_trace.c       | 8 ++++++--
>  kernel/trace/trace.c           | 2 +-
>  kernel/trace/trace_events.c    | 2 +-
>  kernel/trace/trace_printk.c    | 4 ++--
>  kernel/tracepoint.c            | 2 +-
>  7 files changed, 18 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/oprofile/buffer_sync.c b/drivers/oprofile/buffer_sync.c
> index ac27f3d3fbb4..4f61b1b45e0d 100644
> --- a/drivers/oprofile/buffer_sync.c
> +++ b/drivers/oprofile/buffer_sync.c
> @@ -116,7 +116,7 @@ module_load_notify(struct notifier_block *self, unsigned long val, void *data)
>  {
>  #ifdef CONFIG_MODULES
>  	if (val != MODULE_STATE_COMING)
> -		return 0;
> +		return NOTIFY_DONE;
>  
>  	/* FIXME: should we process all CPU buffers ? */
>  	mutex_lock(&buffer_mutex);
> @@ -124,7 +124,7 @@ module_load_notify(struct notifier_block *self, unsigned long val, void *data)
>  	add_event_entry(MODULE_LOADED_CODE);
>  	mutex_unlock(&buffer_mutex);
>  #endif
> -	return 0;
> +	return NOTIFY_OK;
>  }
>  
>  
> diff --git a/kernel/module.c b/kernel/module.c
> index 80c7c09584cf..0c4831f46380 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -3638,9 +3638,10 @@ static int prepare_coming_module(struct module *mod)
>  	if (err)
>  		return err;
>  
> -	blocking_notifier_call_chain(&module_notify_list,
> -				     MODULE_STATE_COMING, mod);
> -	return 0;
> +	ret = blocking_notifier_call_chain(&module_notify_list,
> +					   MODULE_STATE_COMING, mod);
> +	ret = notifier_to_errno(ret);
> +	return ret;
>  }
>  
>  static int unknown_module_param_cb(char *param, char *val, const char *modname,
> @@ -3780,7 +3781,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
>  
>  	err = prepare_coming_module(mod);
>  	if (err)
> -		goto bug_cleanup;
> +		goto coming_cleanup;
>  
>  	/* Module is ready to execute: parsing args may do that. */
>  	after_dashes = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index f92d6ad5e080..18afa75f5208 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1302,10 +1302,11 @@ static int bpf_event_notify(struct notifier_block *nb, unsigned long op,
>  {
>  	struct bpf_trace_module *btm, *tmp;
>  	struct module *mod = module;
> +	int ret = 0;
>  
>  	if (mod->num_bpf_raw_events == 0 ||
>  	    (op != MODULE_STATE_COMING && op != MODULE_STATE_GOING))
> -		return 0;
> +		goto out;
>  
>  	mutex_lock(&bpf_module_mutex);
>  
> @@ -1315,6 +1316,8 @@ static int bpf_event_notify(struct notifier_block *nb, unsigned long op,
>  		if (btm) {
>  			btm->module = module;
>  			list_add(&btm->list, &bpf_trace_modules);
> +		} else {
> +			ret = -ENOMEM;
>  		}
>  		break;
>  	case MODULE_STATE_GOING:
> @@ -1330,7 +1333,8 @@ static int bpf_event_notify(struct notifier_block *nb, unsigned long op,
>  
>  	mutex_unlock(&bpf_module_mutex);
>  
> -	return 0;
> +out:
> +	return notifier_from_errno(ret);
>  }
>  
>  static struct notifier_block bpf_module_nb = {
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 1c80521fd436..6757e7392f1a 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -8685,7 +8685,7 @@ static int trace_module_notify(struct notifier_block *self,
>  		break;
>  	}
>  
> -	return 0;
> +	return NOTIFY_OK;
>  }
>  
>  static struct notifier_block trace_module_nb = {
> diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
> index 0ce3db67f556..32098dbab72e 100644
> --- a/kernel/trace/trace_events.c
> +++ b/kernel/trace/trace_events.c
> @@ -2450,7 +2450,7 @@ static int trace_module_notify(struct notifier_block *self,
>  	mutex_unlock(&trace_types_lock);
>  	mutex_unlock(&event_mutex);
>  
> -	return 0;
> +	return NOTIFY_OK;
>  }
>  
>  static struct notifier_block trace_module_nb = {
> diff --git a/kernel/trace/trace_printk.c b/kernel/trace/trace_printk.c
> index c3fd849d4a8f..d5394e02163f 100644
> --- a/kernel/trace/trace_printk.c
> +++ b/kernel/trace/trace_printk.c
> @@ -95,7 +95,7 @@ static int module_trace_bprintk_format_notify(struct notifier_block *self,
>  		if (val == MODULE_STATE_COMING)
>  			hold_module_trace_bprintk_format(start, end);
>  	}
> -	return 0;
> +	return NOTIFY_OK;
>  }
>  
>  /*
> @@ -173,7 +173,7 @@ __init static int
>  module_trace_bprintk_format_notify(struct notifier_block *self,
>  		unsigned long val, void *data)
>  {
> -	return 0;
> +	return NOTIFY_OK;
>  }
>  static inline const char **
>  find_next_mod_format(int start_index, void *v, const char **fmt, loff_t *pos)
> diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
> index df3ade14ccbd..9ce0a510e6af 100644
> --- a/kernel/tracepoint.c
> +++ b/kernel/tracepoint.c
> @@ -521,7 +521,7 @@ static int tracepoint_module_notify(struct notifier_block *self,
>  	case MODULE_STATE_UNFORMED:
>  		break;
>  	}
> -	return ret;
> +	return notifier_from_errno(ret);
>  }
>  
>  static struct notifier_block tracepoint_module_nb = {