linux-kernel - Re: [PATCH/RFC] RDMA/iwpm: Fix uninitialized error code in iwpm_send

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Date:   Thu, 16 Nov 2017 11:50:48 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Tatyana Nikolova <Tatyana.E.Nikolova@...el.com>,
        Roland Dreier <roland@...estorage.com>,
        Doug Ledford <dledford@...hat.com>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH/RFC] RDMA/iwpm: Fix uninitialized error code in iwpm_send_mapinfo()

On Thu, Nov 16, 2017 at 11:26 AM, Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
> With gcc-4.1.2:
>
>     drivers/infiniband/core/iwpm_util.c: In function ‘iwpm_send_mapinfo’:
>     drivers/infiniband/core/iwpm_util.c:647: warning: ‘ret’ may be used uninitialized in this function
>
> Indeed, if nl_client is not found in any of the scanned has buckets, ret
> will be used uninitialized.
>
> Preinitialize ret to zero to fix this.
>
> Fixes: 30dc5e63d6a5ad24 ("RDMA/core: Add support for iWARP Port Mapper user space service")
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---
> RFC as I have no idea if this can ever happen, and if yes, what's the
> correct behavior to handle it:
>   - return 0,
>   - return an error code,
>   - don't send anything,
>   - anything else?

This looks like a reasonable warning. I don't see on my box with any compiler
version. Do you have a configuration I can use to reproduce it, I'd just like
to see out of curiosity which other compilers report it.

Looking at one caller (iwpm_mapping_info_cb), it seems that we try to make
sure that nl_client is valid first by calling iwpm_valid_client(), and returning
-EINVAL otherwise, so that seems like an appropriate return code if any
caller forgets to test for iwpm_valid_client() first.

      Arnd