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From: Julia Lawall <julia.lawall@inria.fr>
To: Denis Efremov <efremov@linux.com>
Cc: cocci@systeme.lip6.fr, linux-kernel@vger.kernel.org
Subject: Re: [Cocci] [PATCH v6] coccinelle: api: add kvfree script
Date: Mon, 3 Aug 2020 14:18:03 +0200 (CEST)
Message-ID: <alpine.DEB.2.22.394.2008031416301.27678@hadrien> (raw)
In-Reply-To: <a8d8eade-1d98-b8d9-7c66-bd05b22af751@linux.com>



On Mon, 3 Aug 2020, Denis Efremov wrote:

>
>
> On 8/2/20 11:24 PM, Julia Lawall wrote:
> >> +@initialize:python@
> >> +@@
> >> +# low-level memory api
> >> +filter = frozenset(['__vmalloc_area_node'])
> >> +
> >> +def relevant(p):
> >> +    return not (filter & {el.current_element for el in p})
> >
> > Is this used?
>
> I'll remove it in v8. Or do you want me to add iterate_dir_item() in the list?

What is that?

>
> >
> > Otherwise, I think it would be good to not warn about a use of kvfree
> > if that use is reachable from a kvmalloc.  There seems to be such a false
> > positive in fs/btrfs/send.c, on line 1118.
>
> I don't know how to handle this case without position filter.
> It's too complex. In iterate_dir_item() there is:
> buf = kmalloc(buf_len, GFP_KERNEL);
> while(...) {
> 	if (...) {
> 		if (is_vmalloc_addr(buf)) {
> 			vfree(buf);
> 			...
> 		} else {
> 			char *tmp = krealloc(buf, ...);
>
> 			if (!tmp)
> 				kfree(buf);
> 			...
> 		}
> 		if (!buf) {
> 			buf = kvmalloc(buf_len, GFP_KERNEL);
> 			...
> 		}
> 	}
> }
> kvfree(buf);
>
> Adding "when != kvfree(E)" is not enough:
> * E = \(kvmalloc\|kvzalloc\|kvcalloc\|kvzalloc_node\|kvmalloc_node\|
> *       kvmalloc_array\)(...)@k
> 	... when != is_vmalloc_addr(E)
> +	when != kvfree(E)
> 	when any
> * \(kfree\|kzfree\|vfree\|vfree_atomic\)(E)@p

Why not just

@ok exists@
position p;
expression E;
@@

E = kvalloc(...)
...
kvfree@p(...)

Probably that is what you mean by a position filter, but why not add a
position filter?

julia


> >
> > It also seems that when there are both a kmalloc and a vmalloc, there is
> > no warning if kfree or vfree is used.  Is that intentional?
> >
>
> No, I will try to address it in v8.
>
> Regards,
> Denis
>
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Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-05 20:42 [Cocci] [PATCH] " Denis Efremov
2020-06-05 20:51 ` Julia Lawall
2020-06-05 21:15   ` Denis Efremov
2020-06-05 21:19     ` Julia Lawall
2020-06-14  9:03   ` Denis Efremov
2020-06-14  9:17     ` Julia Lawall
2020-06-14  9:24       ` Denis Efremov
2020-06-14 18:36 ` [Cocci] [PATCH v2] " Denis Efremov
2020-07-17 12:00   ` Denis Efremov
2020-07-30 14:01 ` [Cocci] [PATCH v3] " Denis Efremov
2020-07-30 14:05   ` Denis Efremov
2020-07-30 14:07 ` [Cocci] [PATCH v4] " Denis Efremov
2020-07-30 20:15   ` Julia Lawall
2020-07-30 20:38   ` Julia Lawall
2020-07-31  8:31     ` Denis Efremov
2020-07-31  8:48       ` Julia Lawall
2020-07-31 10:47 ` [Cocci] [PATCH v5] " Denis Efremov
2020-07-31 21:00 ` [Cocci] [PATCH v6] " Denis Efremov
2020-08-02 20:24   ` Julia Lawall
2020-08-03 11:33     ` Denis Efremov
2020-08-03 12:18       ` Julia Lawall [this message]
2020-08-03 11:45   ` Denis Efremov
2020-08-03 12:12     ` Julia Lawall
2020-08-03 18:34 ` [Cocci] [PATCH v7] coccinelle: api: add kfree_mismatch script Denis Efremov
2020-09-21 17:15   ` Denis Efremov
2020-10-15 20:48   ` Julia Lawall
2020-10-16  8:54 ` [Cocci] [PATCH v8] " Denis Efremov
2020-10-17 21:17   ` Julia Lawall
     [not found] <3aea12cf-68dc-e140-936f-cfefb2adbc8f@web.de>
2020-08-02  7:09 ` [Cocci] [PATCH v6] coccinelle: api: add kvfree script Julia Lawall

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