linux-kernel - [PATCH 4.1 202/267] selinux: dont waste ebitmap space when importing NetLabel categories

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Date:	Fri, 31 Jul 2015 12:40:53 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Paul Moore <pmoore@...hat.com>
Subject: [PATCH 4.1 202/267] selinux: dont waste ebitmap space when importing NetLabel categories

4.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paul Moore <pmoore@...hat.com>

commit 3324603524925c7727207027d1c15e597412d15e upstream.

At present we don't create efficient ebitmaps when importing NetLabel
category bitmaps.  This can present a problem when comparing ebitmaps
since ebitmap_cmp() is very strict about these things and considers
these wasteful ebitmaps not equal when compared to their more
efficient counterparts, even if their values are the same.  This isn't
likely to cause problems on 64-bit systems due to a bit of luck on
how NetLabel/CIPSO works and the default ebitmap size, but it can be
a problem on 32-bit systems.

This patch fixes this problem by being a bit more intelligent when
importing NetLabel category bitmaps by skipping over empty sections
which should result in a nice, efficient ebitmap.

Signed-off-by: Paul Moore <pmoore@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 security/selinux/ss/ebitmap.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/security/selinux/ss/ebitmap.c
+++ b/security/selinux/ss/ebitmap.c
@@ -153,6 +153,12 @@ int ebitmap_netlbl_import(struct ebitmap
 		if (offset == (u32)-1)
 			return 0;

+		/* don't waste ebitmap space if the netlabel bitmap is empty */
+		if (bitmap == 0) {
+			offset += EBITMAP_UNIT_SIZE;
+			continue;
+		}
+
 		if (e_iter == NULL ||
 		    offset >= e_iter->startbit + EBITMAP_SIZE) {
 			e_prev = e_iter;

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