Re: [PATCH v3 1/2] io_uring: refactor io_uring_allowed()

Paul Moore
2025-02-07T21:42:58Z

On Jan 27, 2025 Hamza Mahfooz <hamzamahfooz@linux.microsoft.com> wrote:
>
> Have io_uring_allowed() return an error code directly instead of
> true/false. This is needed for follow-up work to guard io_uring_setup()
> with LSM.
>
> Cc: Jens Axboe <axboe@kernel.dk>
> Signed-off-by: Hamza Mahfooz <hamzamahfooz@linux.microsoft.com>
> ---
> io_uring/io_uring.c | 21 ++++++++++++++-------
> 1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 7bfbc7c22367..c2d8bd4c2cfc 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -3789,29 +3789,36 @@ 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;

I'd probably just 'return 0;' here as the "allowed_lsm" goto label
doesn't make a lot of sense until patch 2/2, but otherwise this
looks okay to me.

Jens, are you okay with this patch? If yes, can we get an ACK from you?

> 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 0;
> }
>
> 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);
> }
> --
> 2.47.1

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