linux-kernel - Re: [PATCH v13 10/11] SELinux: Add selfattr hooks

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Date:   Thu, 10 Aug 2023 18:24:26 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Casey Schaufler <casey@...aufler-ca.com>, casey@...aufler-ca.com,
        linux-security-module@...r.kernel.org
Cc:     jmorris@...ei.org, serge@...lyn.com, keescook@...omium.org,
        john.johansen@...onical.com, penguin-kernel@...ove.sakura.ne.jp,
        stephen.smalley.work@...il.com, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, mic@...ikod.net, selinux@...r.kernel.org
Subject: Re: [PATCH v13 10/11] SELinux: Add selfattr hooks

On Aug  2, 2023 Casey Schaufler <casey@...aufler-ca.com> wrote:
> 
> Add hooks for setselfattr and getselfattr. These hooks are not very
> different from their setprocattr and getprocattr equivalents, and
> much of the code is shared.
> 
> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
> Cc: selinux@...r.kernel.org
> Cc: Paul Moore <paul@...l-moore.com>
> ---
>  security/selinux/hooks.c | 136 +++++++++++++++++++++++++++++++--------
>  1 file changed, 109 insertions(+), 27 deletions(-)
> 
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index c900813fc8f7..f66a28f672b2 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c

...

> @@ -6449,6 +6466,69 @@ static int selinux_setprocattr(const char *name, void *value, size_t size)
>  	return error;
>  }
>  
> +static int selinux_getselfattr(unsigned int attr, struct lsm_ctx __user *ctx,
> +			       size_t *size, u32 flags)
> +{
> +	char *value;
> +	size_t total_len;
> +	int len;
> +	int rc;
> +
> +	len = selinux_lsm_getattr(attr, current, &value);
> +	if (len < 0)
> +		return len;
> +
> +	total_len = ALIGN(struct_size(ctx, ctx, len), 8);
> +
> +	if (total_len > *size)
> +		rc = -E2BIG;
> +	else if (ctx)
> +		rc = lsm_fill_user_ctx(ctx, value, len, LSM_ID_SELINUX, 0);
> +	else
> +		rc = 1;

I'd probably either set rc to zero when at declaration time and drop
this final else, or explicitly set rc to one here to better fit what
lsm_fill_user_ctx() does on success.  However, the end result is the
same so we can just fix that with a follow-up patch once this is
merged into the lsm/next branch.

> +	kfree(value);
> +	*size = total_len;
> +	if (rc < 0)
> +		return rc;
> +	return 1;
> +}

--
paul-moore.com