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open.2: Fix bug in linkat(2) call example 

AT_EMPTY_PATH works with empty strings (""), but not with NULL
(or at least it's not obvious).

The relevant kernel code is the following:

linux$ sed -n 189,198p fs/namei.c
	result->refcnt = 1;
	/* The empty path is special. */
	if (unlikely(!len)) {
		if (empty)
			*empty = 1;
		if (!(flags & LOOKUP_EMPTY)) {
			putname(result);
			return ERR_PTR(-ENOENT);
		}
	}

Reported-by: Walter Harms <wharms@bfs.de>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Adam Borowski <kilobyte@angband.pl>
Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Alejandro Colomar 2021-05-09 23:39:00 +02:00 committed by Michael Kerrisk
parent 3eb81f5117
commit 1c55195743
1 changed files with 1 additions and 1 deletions
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2
man2/open.2
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@ -824,7 +824,7 @@ fd = open("/path/to/dir", O_TMPFILE | O_RDWR,
/* File I/O on \(aqfd\(aq... */
linkat(fd, NULL, AT_FDCWD, "/path/for/file", AT_EMPTY_PATH);
linkat(fd, "", AT_FDCWD, "/path/for/file", AT_EMPTY_PATH);
/* If the caller doesn\(aqt have the CAP_DAC_READ_SEARCH
capability (needed to use AT_EMPTY_PATH with linkat(2)),