lib: add sys_io_ranges_overlap()

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12033

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

4 files changed, 143 insertions, 0 deletions

diff --git a/lib/util/sys_rw.c b/lib/util/sys_rw.c
index d74395fc409..02aaa871a39 100644
--- a/lib/util/sys_rw.c
+++ b/lib/util/sys_rw.c
@@ -48,6 +48,31 @@ bool sys_valid_io_range(off_t offset, size_t length)
 	return true;
 }
 
+bool sys_io_ranges_overlap(size_t c1, off_t o1,
+			   size_t c2, off_t o2)
+{
+	if (c1 == 0 || c2 == 0) {
+		return false;
+	}
+	if (o2 < o1) {
+		/*
+		 *          o1
+		 *          |····c1····|
+		 *  o2
+		 *  |····c2···| ?
+		 */
+		return (o2 + c2 > o1);
+	} else {
+		/*
+		 *  o1
+		 *  |····c1···|
+		 *          o2
+		 *          |····c2····| ?
+		 */
+		return (o1 + c1 > o2);
+	}
+}
+
 /*******************************************************************
 A read wrapper that will deal with EINTR/EWOULDBLOCK
 ********************************************************************/
diff --git a/lib/util/sys_rw.h b/lib/util/sys_rw.h
index b224ecb30ac..6693d34de57 100644
--- a/lib/util/sys_rw.h
+++ b/lib/util/sys_rw.h
@@ -28,6 +28,8 @@
 struct iovec;
 
 bool sys_valid_io_range(off_t offset, size_t length);
+bool sys_io_ranges_overlap(size_t c1, off_t o1,
+			   size_t c2, off_t o2);
 ssize_t sys_read(int fd, void *buf, size_t count);
 void sys_read_v(int fd, void *buf, size_t count);
 ssize_t sys_write(int fd, const void *buf, size_t count);
diff --git a/lib/util/tests/test_sys_rw.c b/lib/util/tests/test_sys_rw.c
new file mode 100644
index 00000000000..551a6a09bda
--- /dev/null
+++ b/lib/util/tests/test_sys_rw.c
@@ -0,0 +1,110 @@
+/*
+ *  Unix SMB/CIFS implementation.
+ *
+ *  Unit test for sys_rw.c
+ *
+ *  Copyright (C) Ralph Böhme 2021
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <setjmp.h>
+#include <cmocka.h>
+
+#include "lib/replace/replace.h"
+#include "system/dir.h"
+
+#include "lib/util/sys_rw.c"
+
+static void test_sys_io_ranges_overlap(void **state)
+{
+	bool overlap;
+
+	/*
+	 * sys_io_ranges_overlap() args are:
+	 *
+	 * src size, src offset, dst size, dst offset
+	 */
+
+	/* src and dst size 0 => no overlap */
+	overlap = sys_io_ranges_overlap(0, 0, 0, 0);
+	assert_false(overlap);
+
+	/* dst size 0 => no overlap */
+	overlap = sys_io_ranges_overlap(1, 0, 0, 0);
+	assert_false(overlap);
+
+	/* src size 0 => no overlap */
+	overlap = sys_io_ranges_overlap(0, 0, 1, 0);
+	assert_false(overlap);
+
+	/* same range => overlap */
+	overlap = sys_io_ranges_overlap(1, 0, 1, 0);
+	assert_true(overlap);
+
+	/*
+	 * |.|
+	 *   |.|
+	 * src before dst => no overlap
+	 */
+	overlap = sys_io_ranges_overlap(1, 0, 1, 1);
+	assert_false(overlap);
+
+	/*
+	 * |..|
+	 *  |..|
+	 * src into dst => overlap
+	 */
+	overlap = sys_io_ranges_overlap(2, 0, 2, 1);
+	assert_true(overlap);
+
+	/*
+	 * |....|
+	 *  |..|
+	 * src encompasses dst => overlap
+	 */
+	overlap = sys_io_ranges_overlap(4, 0, 1, 2);
+	assert_true(overlap);
+
+
+	/*
+	 *  |..|
+	 * |..|
+	 * dst into src => overlap
+	 */
+	overlap = sys_io_ranges_overlap(2, 1, 2, 0);
+	assert_true(overlap);
+
+	/*
+	 *  |..|
+	 * |....|
+	 * dst encompasses src => overlap
+	 */
+	overlap = sys_io_ranges_overlap(2, 1, 4, 0);
+	assert_true(overlap);
+}
+
+int main(int argc, char **argv)
+{
+	const struct CMUnitTest tests[] = {
+		cmocka_unit_test(test_sys_io_ranges_overlap),
+	};
+
+	cmocka_set_message_output(CM_OUTPUT_SUBUNIT);
+
+	return cmocka_run_group_tests(tests, NULL, NULL);
+}
diff --git a/lib/util/wscript_build b/lib/util/wscript_build
index 2a99e212c5c..b8cfddb3f41 100644
--- a/lib/util/wscript_build
+++ b/lib/util/wscript_build
@@ -356,3 +356,9 @@ else:
                      deps='cmocka replace talloc samba-util',
                      local_include=False,
                      for_selftest=True)
+
+    bld.SAMBA_BINARY('test_sys_rw',
+                     source='tests/test_sys_rw.c',
+                     deps='cmocka replace samba-util',
+                     local_include=False,
+                     for_selftest=True)