linux-kernel - [PATCH 1/5] man-pages: open.2: describe O_BENEATH

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Date:	Mon, 30 Jun 2014 11:28:12 +0100
From:	David Drysdale <drysdale@...gle.com>
To:	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	Meredydd Luff <meredydd@...atehouse.org>,
	Kees Cook <keescook@...omium.org>,
	James Morris <james.l.morris@...cle.com>,
	linux-api@...r.kernel.org, David Drysdale <drysdale@...gle.com>
Subject: [PATCH 1/5] man-pages: open.2: describe O_BENEATH_ONLY flag

Signed-off-by: David Drysdale <drysdale@...gle.com>
---
 man2/open.2 | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/man2/open.2 b/man2/open.2
index 3824ab5be1f0..ba0da01c1a4f 100644
--- a/man2/open.2
+++ b/man2/open.2
@@ -713,7 +713,7 @@ in a fully formed state (using
 as described above).
 .RE
 .IP
-.B O_TMPFILE
+.B O_TMPFILE " (since Linux 3.??)"
 requires support by the underlying filesystem;
 only a subset of Linux filesystems provide that support.
 In the initial implementation, support was provided in
@@ -723,6 +723,31 @@ XFS support was added
 .\" commit ab29743117f9f4c22ac44c13c1647fb24fb2bafe
 in Linux 3.15.
 .TP
+.B O_BENEATH_ONLY
+Ensure that the
+.I pathname
+is beneath the current working directory (for
+.BR open (2))
+or the
+.I dirfd
+(for
+.BR openat (2)).
+If the
+.I pathname
+is absolute or contains a path component of "..", the
+.BR open ()
+fails with the error
+.BR EACCES.
+This occurs even if ".." path component would not actually
+escape the original directory; for example, a
+.I pathname
+of "subdir/../filename" would be rejected.
+Path components that are symbolic links to absolute paths, or that are
+relative paths containing a ".." component, are cause the
+.BR open ()
+operation to fail with the error
+.BR EACCES.
+.TP
 .B O_TRUNC
 If the file already exists and is a regular file and the access mode allows
 writing (i.e., is
@@ -799,7 +824,11 @@ The requested access to the file is not allowed, or search permission
 is denied for one of the directories in the path prefix of
 .IR pathname ,
 or the file did not exist yet and write access to the parent directory
-is not allowed.
+is not allowed, or the
+.B O_BENEATH_ONLY
+flag was specified and the
+.I pathname
+was not beneath the relevant directory.
 (See also
 .BR path_resolution (7).)
 .TP
--
2.0.0.526.g5318336

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