linux-kernel - Re: [PATCH] lsm,io_uring: add LSM hooks for io_uring

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Message-ID: <f72a3036-fe4f-4a94-963a-b994d946d5af@kernel.dk>
Date: Thu, 19 Dec 2024 13:45:41 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>,
 linux-security-module@...r.kernel.org, io-uring@...r.kernel.org
Cc: Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>,
 "Serge E. Hallyn" <serge@...lyn.com>, Pavel Begunkov
 <asml.silence@...il.com>, Stephen Smalley <stephen.smalley.work@...il.com>,
 Ondrej Mosnacek <omosnace@...hat.com>, Thiébaud Weksteen
 <tweek@...gle.com>, Masahiro Yamada <masahiroy@...nel.org>,
 Bram Bonné <brambonne@...gle.com>,
 linux-kernel@...r.kernel.org, selinux@...r.kernel.org
Subject: Re: [PATCH] lsm,io_uring: add LSM hooks for io_uring_setup()

On 12/19/24 1:41 PM, Hamza Mahfooz wrote:
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 06ff41484e29..0922bb0724c0 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -3806,29 +3806,36 @@ static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
>  	return io_uring_create(entries, &p, params);
>  }
>  
> -static inline bool io_uring_allowed(void)
> +static inline int io_uring_allowed(void)
>  {
>  	int disabled = READ_ONCE(sysctl_io_uring_disabled);
>  	kgid_t io_uring_group;
>  
>  	if (disabled == 2)
> -		return false;
> +		return -EPERM;
>  
>  	if (disabled == 0 || capable(CAP_SYS_ADMIN))
> -		return true;
> +		goto allowed_lsm;
>  
>  	io_uring_group = make_kgid(&init_user_ns, sysctl_io_uring_group);
>  	if (!gid_valid(io_uring_group))
> -		return false;
> +		return -EPERM;
> +
> +	if (!in_group_p(io_uring_group))
> +		return -EPERM;
>  
> -	return in_group_p(io_uring_group);
> +allowed_lsm:
> +	return security_uring_allowed();
>  }
>  
>  SYSCALL_DEFINE2(io_uring_setup, u32, entries,
>  		struct io_uring_params __user *, params)
>  {
> -	if (!io_uring_allowed())
> -		return -EPERM;
> +	int ret;
> +
> +	ret = io_uring_allowed();
> +	if (ret)
> +		return ret;
>  
>  	return io_uring_setup(entries, params);
>  }

Please do a prep patch that makes io_uring_allowed() return the actual
error rather than true/false, then the rest of your patch can stand
alone.

-- 
Jens Axboe