Fix integer overflow detection in dd

dd(1) tried to detect whether the seek offset would overflow, but it failed
to account for the case where the provided argument was negative and the
file was a regular file (negative seeks are allowed for character devices).
I fixed it, and added a regression test.

Reported by:	Coverity
CID:		1368659
MFC after:	3 weeks
Sponsored by:	Spectra Logic Corp

3 files changed, 56 insertions, 1 deletions

diff --git a/bin/dd/position.c b/bin/dd/position.c
index 71153f04fe6a..d816716456fe 100644
--- a/bin/dd/position.c
+++ b/bin/dd/position.c
@@ -70,7 +70,7 @@ seek_offset(IO *io)
 	 *
 	 * Bail out if the calculation of a file offset would overflow.
 	 */
-	if ((io->flags & ISCHR) == 0 && n > OFF_MAX / (ssize_t)sz)
+	if ((io->flags & ISCHR) == 0 && (n < 0 || n > OFF_MAX / (ssize_t)sz))
 		errx(1, "seek offsets cannot be larger than %jd",
 		    (intmax_t)OFF_MAX);
 	else if ((io->flags & ISCHR) != 0 && (uint64_t)n > UINT64_MAX / sz)
diff --git a/bin/dd/tests/Makefile b/bin/dd/tests/Makefile
index dd04af915887..4e1f7859f605 100644
--- a/bin/dd/tests/Makefile
+++ b/bin/dd/tests/Makefile
@@ -1,5 +1,10 @@
 # $FreeBSD$
 
+.include <src.opts.mk>
+
+.PATH: ${.CURDIR}/..
+
+ATF_TESTS_SH=	dd2_test
 NETBSD_ATF_TESTS_SH=	dd_test
 
 .include <netbsd-tests.test.mk>
diff --git a/bin/dd/tests/dd2_test.sh b/bin/dd/tests/dd2_test.sh
new file mode 100755
index 000000000000..8e19ab2f8847
--- /dev/null
+++ b/bin/dd/tests/dd2_test.sh
@@ -0,0 +1,50 @@
+#
+# Copyright (c) 2017 Spectra Logic Corporation
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+# ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+# TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+# PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+# BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+# $FreeBSD$
+
+
+atf_test_case seek_overflow
+seek_overflow_head() {
+	atf_set "descr" "dd(1) should reject too-large seek values"
+}
+seek_overflow_body() {
+	touch f.in
+	# Positive tests
+	seek=`echo "2^63 / 4096 - 1" | bc`
+	atf_check -s exit:0 -e ignore dd if=f.in of=f.out bs=4096 seek=$seek
+
+	# Negative tests
+	seek=`echo "2^63 / 4096" | bc`
+	atf_check -s not-exit:0 -e match:"seek offsets cannot be larger than" \
+		dd if=f.in of=f.out bs=4096 seek=$seek
+	atf_check -s not-exit:0 -e match:"seek offsets cannot be larger than" \
+		dd if=f.in of=f.out bs=4096 seek=-1
+}
+
+atf_init_test_cases()
+{
+        atf_add_test_case seek_overflow
+}