linux-kernel - Re: [PATCH v12 8/11] Smack: implement setselfattr and getselfattr hooks

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Date:   Thu, 29 Jun 2023 22:14:44 -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
Subject: Re: [PATCH v12 8/11] Smack: implement setselfattr and getselfattr  hooks

On Jun 29, 2023 Casey Schaufler <casey@...aufler-ca.com> wrote:
> 
> Implement Smack support for security_[gs]etselfattr.
> Refactor the setprocattr hook to avoid code duplication.
> 
> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
> ---
>  security/smack/smack_lsm.c | 106 +++++++++++++++++++++++++++++++++++--
>  1 file changed, 101 insertions(+), 5 deletions(-)
> 
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index cf847cfe5ed8..4a84639e9db9 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c

...

> @@ -3629,6 +3668,61 @@ static int smack_setprocattr(const char *name, void *value, size_t size)
>  	return size;
>  }
>  
> +/**
> + * smack_setselfattr - Set a Smack process attribute
> + * @attr: which attribute to set
> + * @ctx: buffer containing the data
> + * @size: size of @ctx
> + * @flags: unused
> + *
> + * Fill the passed user space @ctx with the details of the requested
> + * attribute.
> + *
> + * Returns 0 on success, an error code otherwise.
> + */
> +static int smack_setselfattr(unsigned int attr, struct lsm_ctx __user *ctx,
> +			     size_t size, u32 flags)
> +{
> +	struct lsm_ctx *lctx;
> +	int rc;
> +
> +	lctx = kmalloc(size, GFP_KERNEL);
> +	if (lctx == NULL)
> +		return -ENOMEM;
> +
> +	if (copy_from_user(lctx, ctx, size))
> +		rc = -EFAULT;
> +	else if (lctx->ctx_len > size)
> +		rc = -E2BIG;
> +	else
> +		rc = do_setattr(attr, lctx->ctx, lctx->ctx_len);
> +
> +	kfree(lctx);
> +	if (rc > 0)
> +		return 0;
> +	return rc;
> +}
> +
> +/**
> + * smack_setprocattr - Smack process attribute setting
> + * @name: the name of the attribute in /proc/.../attr
> + * @value: the value to set
> + * @size: the size of the value
> + *
> + * Sets the Smack value of the task. Only setting self
> + * is permitted and only with privilege
> + *
> + * Returns the length of the smack label or an error code
> + */
> +static int smack_setprocattr(const char *name, void *value, size_t size)
> +{
> +	int attr = lsm_name_to_attr(name);
> +
> +	if (attr == LSM_ATTR_UNDEF)

That should be '(attr != LSM_ATTR_UNDEF)', right?

> +		return do_setattr(attr, value, size);
> +	return -EINVAL;
> +}
> +
>  /**
>   * smack_unix_stream_connect - Smack access on UDS
>   * @sock: one sock
> @@ -4939,6 +5033,8 @@ static struct security_hook_list smack_hooks[] __ro_after_init = {
>  
>  	LSM_HOOK_INIT(d_instantiate, smack_d_instantiate),
>  
> +	LSM_HOOK_INIT(getselfattr, smack_getselfattr),
> +	LSM_HOOK_INIT(setselfattr, smack_setselfattr),
>  	LSM_HOOK_INIT(getprocattr, smack_getprocattr),
>  	LSM_HOOK_INIT(setprocattr, smack_setprocattr),
>  
> -- 
> 2.40.1

--
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