net/smc: Fix preinitialization of buf_desc in __smc_buf_create()

With gcc-4.1.2:

    net/smc/smc_core.c: In function ‘__smc_buf_create’:
    net/smc/smc_core.c:567: warning: ‘bufsize’ may be used uninitialized in this function

Indeed, if the for-loop is never executed, bufsize is used
uninitialized.  In addition, buf_desc is stored for later use, while it
is still a NULL pointer.

Before, error handling was done by checking if buf_desc is non-NULL.
The cleanup changed this to an error check, but forgot to update the
preinitialization of buf_desc to an error pointer.

Update the preinitializatin of buf_desc to fix this.

Fixes: b33982c3a6838d13 ("net/smc: cleanup function __smc_buf_create()")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
I don't know if this can ever happen, but the old code handled it.
---
 net/smc/smc_core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

On Thu, Nov 16, 2017 at 12:22 PM, Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> With gcc-4.1.2:
>
>     net/smc/smc_core.c: In function ‘__smc_buf_create’:
>     net/smc/smc_core.c:567: warning: ‘bufsize’ may be used uninitialized in this function
>
> Indeed, if the for-loop is never executed, bufsize is used
> uninitialized.  In addition, buf_desc is stored for later use, while it
> is still a NULL pointer.
>
> Before, error handling was done by checking if buf_desc is non-NULL.
> The cleanup changed this to an error check, but forgot to update the
> preinitialization of buf_desc to an error pointer.
>
> Update the preinitializatin of buf_desc to fix this.
>
> Fixes: b33982c3a6838d13 ("net/smc: cleanup function __smc_buf_create()")
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> ---
> I don't know if this can ever happen, but the old code handled it.

Acked-by: Arnd Bergmann <arnd@arndb.de>

This one I could reproduce with gcc-4.1 on x86, but not gcc-4.2 or higher.

On 11/16/2017 12:22 PM, Geert Uytterhoeven wrote:
> With gcc-4.1.2:
> 
>     net/smc/smc_core.c: In function ‘__smc_buf_create’:
>     net/smc/smc_core.c:567: warning: ‘bufsize’ may be used uninitialized in this function
> 
> Indeed, if the for-loop is never executed, bufsize is used
> uninitialized.  In addition, buf_desc is stored for later use, while it
> is still a NULL pointer.
> 
> Before, error handling was done by checking if buf_desc is non-NULL.
> The cleanup changed this to an error check, but forgot to update the
> preinitialization of buf_desc to an error pointer.
> 
> Update the preinitializatin of buf_desc to fix this.
> 
> Fixes: b33982c3a6838d13 ("net/smc: cleanup function __smc_buf_create()")
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> ---
> I don't know if this can ever happen, but the old code handled it.

The for-loop is at least executed once; thus there is no real problem.
Nevertheless the warning is ugly, and the current initialization with NULL
meaningless after the smc_buf cleanup. Therefore I add your patch to my list of
coming smc patches. Thanks!

> ---
>  net/smc/smc_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
> index 2578fbd95664af84..453c54467082d93f 100644
> --- a/net/smc/smc_core.c
> +++ b/net/smc/smc_core.c
> @@ -562,7 +562,7 @@ static int __smc_buf_create(struct smc_sock *smc, bool is_rmb)
>  {
>  	struct smc_connection *conn = &smc->conn;
>  	struct smc_link_group *lgr = conn->lgr;
> -	struct smc_buf_desc *buf_desc = NULL;
> +	struct smc_buf_desc *buf_desc = ERR_PTR(-ENOMEM);
>  	struct list_head *buf_list;
>  	int bufsize, bufsize_short;
>  	int sk_buf_size;
>