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From:   Al Viro <viro@zeniv.linux.org.uk>
To:     "Eric W. Biederman" <ebiederm@xmission.com>
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Subject: Re: [PATCH v2 09/24] file: Replace fcheck_files with
 files_lookup_fd_rcu
Message-ID: <20201207224656.GC4115853@ZenIV.linux.org.uk>
References: <87r1on1v62.fsf@x220.int.ebiederm.org>
 <20201120231441.29911-9-ebiederm@xmission.com>
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On Fri, Nov 20, 2020 at 05:14:26PM -0600, Eric W. Biederman wrote:

>  /*
>   * Check whether the specified fd has an open file.
>   */
> -#define fcheck(fd)	fcheck_files(current->files, fd)
> +#define fcheck(fd)	files_lookup_fd_rcu(current->files, fd)

Huh?
fs/file.c:1113: file = fcheck(oldfd);
	dup3(), under ->file_lock, no rcu_read_lock() in sight

fs/locks.c:2548:                f = fcheck(fd);
	fcntl_setlk(), ditto

fs/locks.c:2679:                f = fcheck(fd);
	fcntl_setlk64(), ditto

fs/notify/dnotify/dnotify.c:330:        f = fcheck(fd);
	fcntl_dirnotify(); this one _is_ under rcu_read_lock().


IOW, unless I've missed something earlier in the series, this is wrong.