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

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Date:   Fri, 30 Jun 2023 10:10:30 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     Paul Moore <paul@...l-moore.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,
        Casey Schaufler <casey@...aufler-ca.com>
Subject: Re: [PATCH v12 8/11] Smack: implement setselfattr and getselfattr
 hooks

On 6/29/2023 7:14 PM, Paul Moore wrote:
> 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?

Yes, you're right. I'll fix and respin.

>
>> +		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
> --
> paul-moore.com