Re: [PATCH v6] coccinelle: semantic code search for missing put_device()

[Julia Lawall]

On Sat, 16 Feb 2019, Wen Yang wrote:

> The of_find_device_by_node() takes a reference to the underlying device
> structure, we should release that reference.
> The implementation of this semantic code search is:
> In a function, for a local variable obtained by of_find_device_by_node(),
> a, if it is released by a function such as
>    put_device()/of_dev_put()/platform_device_put() after the last use,
>    it is considered that there is no reference leak;
> b, if it is passed back to the caller via
>    dev_get_drvdata()/platform_get_drvdata()/get_device(), etc., the
>    reference will be released in other functions, and the current function
>    also considers that there is no reference leak;
> c, for the rest of the situation, the current function should release the
>    reference by calling put_device, this code search will report an error
>    with a specific confidence.
>
> By using this semantic code search, we have found some issues, such as:
> commit 11907e9d3533 ("ASoC: fsl-asoc-card: fix object reference leaks in
> fsl_asoc_card_probe")
> commit a12085d13997 ("mtd: rawnand: atmel: fix possible object reference
> leak")
> commit 11493f26856a ("mtd: rawnand: jz4780: fix possible object reference
> leak")
>
> There are still dozens of reference leaks in the current kernel code.
>
> Further, for the case of b, the object returned to other functions may also
> have a reference leak, we will continue to develop other cocci scripts to
> further check the reference leak.
>
> Signed-off-by: Wen Yang <yellowriver2010@xxxxxxxxxxx>
> Reviewed-by: Julia Lawall <Julia.Lawall@xxxxxxx>

Acked-by: Julia Lawall <julia.lawall@xxxxxxx>

> Reviewed-by: Markus Elfring <Markus.Elfring@xxxxxx>
> Cc: Julia Lawall <Julia.Lawall@xxxxxxx>
> Cc: Gilles Muller <Gilles.Muller@xxxxxxx>
> Cc: Nicolas Palix <nicolas.palix@xxxxxxx>
> Cc: Michal Marek <michal.lkml@xxxxxxxxxxx>
> Cc: Markus Elfring <Markus.Elfring@xxxxxx>
> Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
> Cc: Wen Yang <wen.yang99@xxxxxxxxxx>
> Cc: cheng.shengyu@xxxxxxxxxx
> Cc: cocci@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> ---
> v6:
> - to be double sure, replace &id->dev with (T)(&id->dev).
> - long string literals can be accepted because of error message search concerns around a tool like grep
> v5:
> - exchange the word patch by code search.
> - add a SPDX identifier.
> - a split string literal can be unwanted.
> - Change the content of the reported information.
> v4:
> - add Masahiro Yamada
> - omit a blank line
> - split the long message parameter
> - reduce the number of metavariables
> - Describe the implementation of the semantic patch,
>   explain the scenarios it can detect,
>   and further software development considerations.
> v3:
> - reduction of a bit of redundant C code within SmPL search specifications.
> - consider the message construction without using the extra Python variable msg.
> v2:
> - put exists after search, and then drop the when exists below.
> - should not use the same e as in the when's below.
> - Make a new type metavariable and use it to put a cast on the result of platform_get_drvdata.
>
>  scripts/coccinelle/free/put_device.cocci | 55 ++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
>  create mode 100644 scripts/coccinelle/free/put_device.cocci
>
> diff --git a/scripts/coccinelle/free/put_device.cocci b/scripts/coccinelle/free/put_device.cocci
> new file mode 100644
> index 000000000000..96e2508c0be1
> --- /dev/null
> +++ b/scripts/coccinelle/free/put_device.cocci
> @@ -0,0 +1,55 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/// Find missing put_device for every of_find_device_by_node.
> +///
> +// Confidence: Moderate
> +// Copyright: (C) 2018-2019 Wen Yang, ZTE.
> +// Comments:
> +// Options: --no-includes --include-headers
> +
> +virtual report
> +virtual org
> +
> +@search exists@
> +local idexpression id;
> +expression x,e,e1;
> +position p1,p2;
> +type T,T1,T2;
> +@@
> +
> +id = of_find_device_by_node@p1(x)
> +... when != e = id
> +if (id == NULL || ...) { ... return ...; }
> +... when != put_device(&id->dev)
> +    when != platform_device_put(id)
> +    when != of_dev_put(id)
> +    when != if (id) { ... put_device(&id->dev) ... }
> +    when != e1 = (T)id
> +    when != e1 = (T)(&id->dev)
> +    when != e1 = get_device(&id->dev)
> +    when != e1 = (T)platform_get_drvdata(id)
> +(
> +  return
> +(    id
> +|    (T1)dev_get_drvdata(&id->dev)
> +|    (T2)platform_get_drvdata(id)
> +);
> +| return@p2 ...;
> +)
> +
> +@script:python depends on report@
> +p1 << search.p1;
> +p2 << search.p2;
> +@@
> +
> +coccilib.report.print_report(p2[0],
> +			     "ERROR: missing put_device; call of_find_device_by_node on line "
> +                             + p1[0].line
> +                             + ", but without a corresponding object release within this function.")
> +
> +@script:python depends on org@
> +p1 << search.p1;
> +p2 << search.p2;
> +@@
> +
> +cocci.print_main("of_find_device_by_node", p1)
> +cocci.print_secs("needed put_device", p2)
> --
> 2.20.1
>
>