linux-kernel - Re: [PATCH] security: Use || instead of

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Message-ID: <20160602141349.GA26954@mail.hallyn.com>
Date:	Thu, 2 Jun 2016 09:13:49 -0500
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Rui Teng <rui.teng@...ux.vnet.ibm.com>
Cc:	serge.hallyn@...onical.com, james.l.morris@...cle.com,
	serge@...lyn.com, linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH] security: Use || instead of | for boolean expressions

On Wed, Jun 01, 2016 at 02:03:02PM +0800, Rui Teng wrote:
> Sparse spits out the following warning:
> 	security/commoncap.c:989:41: warning: dubious: !x | y
> 
> Bitwise and logical are equivalent here, but logical was intended.
> Replacing the bit-wise '|' with the boolean '||' silences the sparse warning.

Hi,

this looks ok, but I'm worried by

> The generated code for both cases is the same.

That cannot be.  The logical result should be the same, but the
generated code cannot be.

I'm cc:ing Andy as this code came in with his patch.  Is there an
actual reason for having used bitwise here?

thanks,
-serge

> Signed-off-by: Rui Teng <rui.teng@...ux.vnet.ibm.com>
> ---
>  security/commoncap.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/security/commoncap.c b/security/commoncap.c
> index e7fadde..8f6fb24 100644
> --- a/security/commoncap.c
> +++ b/security/commoncap.c
> @@ -976,7 +976,7 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
>  
>  	case PR_CAP_AMBIENT:
>  		if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
> -			if (arg3 | arg4 | arg5)
> +			if (arg3 || arg4 || arg5)
>  				return -EINVAL;
>  
>  			new = prepare_creds();
> @@ -986,7 +986,7 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
>  			return commit_creds(new);
>  		}
>  
> -		if (((!cap_valid(arg3)) | arg4 | arg5))
> +		if (((!cap_valid(arg3)) || arg4 || arg5))
>  			return -EINVAL;
>  
>  		if (arg2 == PR_CAP_AMBIENT_IS_SET) {
> -- 
> 2.7.4