From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Ludovic BARRE <ludovic.barre@st.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
Cyrille Pitchen <cyrille.pitchen@wedev4u.fr>,
Marek Vasut <marek.vasut@gmail.com>,
Boris Brezillon <boris.brezillon@free-electrons.com>,
Alexandre Torgue <alexandre.torgue@st.com>,
Richard Weinberger <richard@nod.at>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
MTD Maling List <linux-mtd@lists.infradead.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Maxime Coquelin <mcoquelin.stm32@gmail.com>,
Brian Norris <computersforpeace@gmail.com>,
David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH] mtd: spi-nor: stm32-quadspi: avoid unintialized return code
Date: Thu, 14 Sep 2017 17:24:33 +0200 [thread overview]
Message-ID: <CAMuHMdV6G8WeWgjPcYrMYiSiu=atOSkFZHxwvSsvcwmsv9J+oA@mail.gmail.com> (raw)
In-Reply-To: <feb9b51e-7b77-d184-2ed6-f0d33a06bbcf@st.com>
Hi Ludovic,
On Thu, Sep 14, 2017 at 5:13 PM, Ludovic BARRE <ludovic.barre@st.com> wrote:
> On 09/14/2017 03:38 PM, Geert Uytterhoeven wrote:
>> On Thu, Sep 14, 2017 at 1:06 PM, Arnd Bergmann <arnd@arndb.de> wrote:
>>> If we send zero-length data to stm32_qspi_tx_poll() on older
>>> compiler versions such as gcc-4.6, we get warned that the
>>> return code is uninitialized:
>>>
>>> drivers/mtd/spi-nor/stm32-quadspi.c:248:2: error: ‘ret’ may be used
>>> uninitialized in this function [-Werror=uninitialized]
>>>
>>> On newer compiler versions, the return code is always zero
>>> in this case, as the local variable gets optimized away and
>>> is assumed to be zero after the loop completes without error.
>>>
>>> This changes the function to instead return -EINVAL if it
>>> ever gets called with a zero length buffer.
>>>
>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82203
>>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>>> ---
>>> drivers/mtd/spi-nor/stm32-quadspi.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/mtd/spi-nor/stm32-quadspi.c
>>> b/drivers/mtd/spi-nor/stm32-quadspi.c
>>> index 86c0931543c5..711cfe7aa4bf 100644
>>> --- a/drivers/mtd/spi-nor/stm32-quadspi.c
>>> +++ b/drivers/mtd/spi-nor/stm32-quadspi.c
>>> @@ -227,7 +227,7 @@ static int stm32_qspi_tx_poll(struct stm32_qspi
>>> *qspi,
>>> void (*tx_fifo)(u8 *, void __iomem *);
>>> u32 len = cmd->len, sr;
>>> u8 *buf = cmd->buf;
>>> - int ret;
>>> + int ret = -EINVAL;
>>>
>>> if (cmd->qspimode == CCR_FMODE_INDW)
>>> tx_fifo = stm32_qspi_write_fifo;
>>
>>
>> See also "[PATCH] mtd: spi-nor: stm32-quadspi: Fix uninitialized error
>> return code"
>> (https://patchwork.kernel.org/patch/9842173/)
>
> hi Arnd, Geert
>
> sorry, I was forgot this thread while my holidays
>
> Geert: what do you mean like "similar bugs in the future" in "If you
> initialized ret at the beginning, you lose the ability to catch newly
> introduced similar bugs in the future."
If you pre-initialize ret at the top, you loose the ability of the compiler
to detect at compile-time if ret is never written to later. It will just return
-EINVAL at runtime.
With my version, if the code is modified later and another "return ret" is
added, the compiler will detect if there's a code path that forgets
to assign a value to ret.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
next prev parent reply other threads:[~2017-09-14 15:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-14 11:06 [PATCH] mtd: spi-nor: stm32-quadspi: avoid unintialized return code Arnd Bergmann
2017-09-14 12:38 ` Ludovic BARRE
2017-09-14 13:38 ` Geert Uytterhoeven
2017-09-14 15:13 ` Ludovic BARRE
2017-09-14 15:24 ` Geert Uytterhoeven [this message]
2017-09-14 16:55 ` Ludovic BARRE
2017-09-14 21:38 ` Arnd Bergmann
2017-09-15 7:59 ` Ludovic BARRE
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAMuHMdV6G8WeWgjPcYrMYiSiu=atOSkFZHxwvSsvcwmsv9J+oA@mail.gmail.com' \
--to=geert@linux-m68k.org \
--cc=alexandre.torgue@st.com \
--cc=arnd@arndb.de \
--cc=boris.brezillon@free-electrons.com \
--cc=computersforpeace@gmail.com \
--cc=cyrille.pitchen@wedev4u.fr \
--cc=dwmw2@infradead.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mtd@lists.infradead.org \
--cc=ludovic.barre@st.com \
--cc=marek.vasut@gmail.com \
--cc=mcoquelin.stm32@gmail.com \
--cc=richard@nod.at \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).