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From: Miroslav Benes <mbenes@suse.cz>
To: Petr Mladek <pmladek@suse.com>
Cc: Jiri Kosina <jikos@kernel.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Jason Baron <jbaron@akamai.com>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Evgenii Shatokhin <eshatokhin@virtuozzo.com>,
	live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
	Jessica Yu <jeyu@kernel.org>
Subject: Re: [PATCH v13 04/12] livepatch: Consolidate klp_free functions
Date: Wed, 21 Nov 2018 14:59:29 +0100 (CET)
Message-ID: <alpine.LSU.2.21.1811211450280.7578@pobox.suse.cz> (raw)
In-Reply-To: <20181015123713.25868-5-pmladek@suse.com>

> -/*
> - * Free all functions' kobjects in the array up to some limit. When limit is
> - * NULL, all kobjects are freed.
> - */
> -static void klp_free_funcs_limited(struct klp_object *obj,
> -				   struct klp_func *limit)
> +static void klp_free_funcs(struct klp_object *obj)
>  {
>  	struct klp_func *func;
>  
> -	for (func = obj->funcs; func->old_name && func != limit; func++)
> -		kobject_put(&func->kobj);
> +	klp_for_each_func(obj, func) {
> +		/* Might be called from klp_init_patch() error path. */
> +		if (func->kobj.state_initialized)
> +			kobject_put(&func->kobj);
> +	}
>  }

I have not noticed till today, but state_initialized is probably not the 
best idea. kobject_init_and_add() sets it to 1 in kobject_init() part but 
then _add() is called which could result in error. So we would end up with 
state_initialized equal to 1 and kobject reference equal to 0. Later call 
to kobject_put() in klp_free_funcs() (or elsewhere) would not call 
->release method, because refcount would be 0 by then.

I think that all would end up well, but that does not mean we should not 
fix it.

We could use state_in_sysfs, but I do not think it guarantees anything. 
Both are internal states and maybe we should not rely on them.

So kref_read() and check the reference?

Miroslav

  parent reply index

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-15 12:37 [PATCH v13 00/12] livepatch: Atomic replace feature Petr Mladek
2018-10-15 12:37 ` [PATCH v13 01/12] livepatch: Change void *new_func -> unsigned long new_addr in struct klp_func Petr Mladek
2018-10-15 12:37 ` [PATCH v13 02/12] livepatch: Helper macros to define livepatch structures Petr Mladek
2018-10-17 18:17   ` Josh Poimboeuf
2018-10-18 11:11     ` Petr Mladek
2018-10-18 12:58       ` Josh Poimboeuf
2018-10-24 11:28         ` Petr Mladek
2018-11-21 12:17           ` Miroslav Benes
2018-10-15 12:37 ` [PATCH v13 03/12] livepatch: Shuffle klp_enable_patch()/klp_disable_patch() code Petr Mladek
2018-10-15 12:37 ` [PATCH v13 04/12] livepatch: Consolidate klp_free functions Petr Mladek
2018-10-17 18:22   ` Josh Poimboeuf
2018-10-18 11:40     ` Petr Mladek
2018-11-21 13:59   ` Miroslav Benes [this message]
2018-11-21 14:40     ` Petr Mladek
2018-10-15 12:37 ` [PATCH v13 05/12] livepatch: Refuse to unload only livepatches available during a forced transition Petr Mladek
2018-10-17 18:35   ` Josh Poimboeuf
2018-10-18 12:09     ` Petr Mladek
2018-10-18 13:00       ` Josh Poimboeuf
2018-10-15 12:37 ` [PATCH v13 06/12] livepatch: Simplify API by removing registration step Petr Mladek
2018-10-17 19:06   ` Josh Poimboeuf
2018-10-18 12:33     ` Petr Mladek
2018-10-15 12:37 ` [PATCH v13 07/12] livepatch: Use lists to manage patches, objects and functions Petr Mladek
2018-10-17 20:31   ` Josh Poimboeuf
2018-10-18 12:34     ` Petr Mladek
2018-10-15 12:37 ` [PATCH v13 08/12] livepatch: Add atomic replace Petr Mladek
2018-11-23 12:00   ` Miroslav Benes
2018-10-15 12:37 ` [PATCH v13 09/12] livepatch: Remove Nop structures when unused Petr Mladek
2018-10-17 20:48   ` Josh Poimboeuf
2018-10-18 12:40     ` Petr Mladek
2018-10-15 12:37 ` [PATCH v13 10/12] livepatch: Atomic replace and cumulative patches documentation Petr Mladek
2018-10-15 12:37 ` [PATCH v13 11/12] livepatch: Remove ordering and refuse loading conflicting patches Petr Mladek
2018-10-15 12:37 ` [PATCH v13 12/12] selftests/livepatch: introduce tests Petr Mladek
2018-10-15 19:46   ` Joe Lawrence
2018-10-17 20:48   ` Josh Poimboeuf
2018-10-18 13:34 ` [PATCH v13 00/12] livepatch: Atomic replace feature Josh Poimboeuf

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