linux-kernel - Re: [PATCH] fs/fcntl: return -ESRCH in f

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Message-ID: <5941E8BF.2070304@huawei.com>
Date:   Thu, 15 Jun 2017 09:54:07 +0800
From:   zhong jiang <zhongjiang@...wei.com>
To:     Jeff Layton <jlayton@...hat.com>
CC:     <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <jslaby@...e.cz>, <bfields@...ldses.org>,
        <viro@...iv.linux.org.uk>, <dhowells@...hat.com>
Subject: Re: [PATCH] fs/fcntl: return -ESRCH in f_setown when pid/pgid can't
 be found

yes,  look good to me.

but I found the another issue.  if the pass argument  is -1.  by the spec describe,
type should be assigned to PIDTYPE_MAX,  Do you think that it deserve another patch ?

Thanks
zhongjiang

On 2017/6/14 22:52, Jeff Layton wrote:
> The current implementation of F_SETOWN doesn't properly vet the argument
> passed in. It never returns an error. If the argument doesn't specify a
> valid pid/pgid, then we just end up cleaning out the file->f_owner
> structure.
>
> What we really want is to only clean that out only in the case where
> userland passed in an argument of 0. For anything else, we want to
> return ESRCH if it doesn't refer to a valid pid.
>
> The relevant POSIX spec page is here:
>
>     http://pubs.opengroup.org/onlinepubs/9699919799/functions/fcntl.html
>
> Cc: Jiri Slaby <jslaby@...e.cz>
> Cc: zhong jiang <zhongjiang@...wei.com>
> Signed-off-by: Jeff Layton <jlayton@...hat.com>
> ---
>  fs/fcntl.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/fs/fcntl.c b/fs/fcntl.c
> index 693322e28751..afed3b364979 100644
> --- a/fs/fcntl.c
> +++ b/fs/fcntl.c
> @@ -112,8 +112,9 @@ EXPORT_SYMBOL(__f_setown);
>  int f_setown(struct file *filp, unsigned long arg, int force)
>  {
>  	enum pid_type type;
> -	struct pid *pid;
> -	int who = arg;
> +	struct pid *pid = NULL;
> +	int who = arg, ret = 0;
> +
>  	type = PIDTYPE_PID;
>  	if (who < 0) {
>  		/* avoid overflow below */
> @@ -123,12 +124,19 @@ int f_setown(struct file *filp, unsigned long arg, int force)
>  		type = PIDTYPE_PGID;
>  		who = -who;
>  	}
> +
>  	rcu_read_lock();
> -	pid = find_vpid(who);
> -	__f_setown(filp, pid, type, force);
> +	if (who) {
> +		pid = find_vpid(who);
> +		if (!pid)
> +			ret = -ESRCH;
> +	}
> +
> +	if (!ret)
> +		__f_setown(filp, pid, type, force);
>  	rcu_read_unlock();
>  
> -	return 0;
> +	return ret;
>  }
>  EXPORT_SYMBOL(f_setown);
>