linux-kernel - endian bitshift defects [ was: staging: fusb302: don't bitshift _

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Date:   Fri, 16 Jun 2017 15:44:37 -0700
From:   Joe Perches <joe@...ches.com>
To:     Frans Klaver <fransklaver@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        kernel-janitors <kernel-janitors@...r.kernel.org>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Yueyao Zhu <yueyao.zhu@...il.com>,
        Rui Miguel Silva <rmfrfs@...il.com>,
        Guru Das Srinagesh <gurooodas@...il.com>,
        Javier Martinez Canillas <javier@...hile0.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: endian bitshift defects [ was: staging: fusb302: don't bitshift
 __le16 type ]

On Fri, 2017-06-16 at 19:45 +0200, Frans Klaver wrote:
> The header field in struct pd_message is declared as an __le16 type. The
> data in the message is supposed to be little endian. This means we don't
> have to go and shift the individual bytes into position when we're
> filling the buffer, we can just copy the contents right away. As an
> added benefit we don't get fishy results on big endian systems anymore.

Thanks for pointing this out.

There are several instances of this class of error.

Here's a cocci script to find them.

This is best used with cocci's --all-includes option like:

$ spatch --all-includes --very-quiet --sp-file lebe_bitshifts.cocci .
[ many defects...]

$ cat lebe_bitshifts.cocci
@@
typedef __le16, __le32, __le64,  __be16, __be32, __be64;
{ __le16, __le32, __le64,  __be16, __be32, __be64 } a;
expression b;
@@

*	a << b

@@
{ __le16, __le32, __le64,  __be16, __be32, __be64 } a;
expression b;
@@

*	a <<= b

@@
{ __le16, __le32, __le64,  __be16, __be32, __be64 } a;
expression b;
@@

*	a >> b

@@
{ __le16, __le32, __le64,  __be16, __be32, __be64 } a;
expression b;
@@

*	a >>= b
$