linux-kernel - Re: [PATCH 2/8] ucounts: Fix set_cred

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Date:   Tue, 15 Feb 2022 12:10:33 +0100
From:   Michal Koutný <mkoutny@...e.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     linux-kernel@...r.kernel.org, Alexey Gladkov <legion@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Shuah Khan <shuah@...nel.org>,
        Christian Brauner <brauner@...nel.org>,
        Solar Designer <solar@...nwall.com>,
        Ran Xiaokai <ran.xiaokai@....com.cn>,
        containers@...ts.linux-foundation.org, stable@...r.kernel.org
Subject: Re: [PATCH 2/8] ucounts: Fix set_cred_ucounts

On Thu, Feb 10, 2022 at 08:13:18PM -0600, "Eric W. Biederman" <ebiederm@...ssion.com> wrote:
> diff --git a/kernel/cred.c b/kernel/cred.c
> index 473d17c431f3..933155c96922 100644
> --- a/kernel/cred.c
> +++ b/kernel/cred.c
> @@ -665,21 +665,16 @@ EXPORT_SYMBOL(cred_fscmp);
>  
>  int set_cred_ucounts(struct cred *new)
>  {
> -	struct task_struct *task = current;
> -	const struct cred *old = task->real_cred;
>  	struct ucounts *new_ucounts, *old_ucounts = new->ucounts;
>  
> -	if (new->user == old->user && new->user_ns == old->user_ns)
> -		return 0;
> -
>  	/*
>  	 * This optimization is needed because alloc_ucounts() uses locks
>  	 * for table lookups.
>  	 */
> -	if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid))
> +	if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->uid))
>  		return 0;
>  
> -	if (!(new_ucounts = alloc_ucounts(new->user_ns, new->euid)))
> +	if (!(new_ucounts = alloc_ucounts(new->user_ns, new->uid)))
>  		return -EAGAIN;
>  
>  	new->ucounts = new_ucounts;

Reviewed-by: Michal Koutný <mkoutny@...e.com>