[Libguestfs] [nbdkit PATCH 1/3] sh: Fix flags when none are present

[Eric Blake]

fbuf was used uninitialized, which meant we printed garbage data from
the heap when flags was 0.  Update the test to prevent regressions.

Fixes: bcac9c40
Signed-off-by: Eric Blake <eblake at redhat.com>
---
 plugins/sh/sh.c     |  2 ++
 tests/test-shell.sh | 15 +++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/plugins/sh/sh.c b/plugins/sh/sh.c
index aeb01918..737c38cf 100644
--- a/plugins/sh/sh.c
+++ b/plugins/sh/sh.c
@@ -453,6 +453,8 @@ flags_string (uint32_t flags, char *buf, size_t len)
 {
   bool comma = false;

+  buf[0] = '\0';
+
   if (flags & NBDKIT_FLAG_FUA)
     flag_append ("fua", &comma, &buf, &len);

diff --git a/tests/test-shell.sh b/tests/test-shell.sh
index a744b275..53c0b943 100755
--- a/tests/test-shell.sh
+++ b/tests/test-shell.sh
@@ -42,6 +42,11 @@ case "$1" in
         ;;

     pwrite)
+	case $5 in
+	    '' | fua) ;;
+	    *) 	echo "garbage flags: '$5'" >&2
+		exit 1;
+	esac
         dd oflag=seek_bytes conv=notrunc seek=$4 of=$f || exit 1
         ;;
     can_write)
@@ -54,6 +59,11 @@ case "$1" in
         ;;

     trim)
+	case $5 in
+	    '' | fua) ;;
+	    *) 	echo "garbage flags: '$5'" >&2
+		exit 1;
+	esac
         fallocate -p -o $4 -l $3 -n $f
         ;;
     can_trim)
@@ -62,6 +72,11 @@ case "$1" in
         ;;

     zero)
+	case $5 in
+	    '' | fua | may_trim | fua,may_trim ) ;;
+	    *) 	echo "garbage flags: '$5'" >&2
+		exit 1;
+	esac
         fallocate -z -o $4 -l $3 -n $f
         ;;
     can_zero)
-- 
2.20.1