mergegcc9

1 files changed, 15 insertions, 6 deletions

diff --git a/usr/src/boot/lib/libstand/zfs/zfs.c b/usr/src/boot/lib/libstand/zfs/zfs.c
index 665d0b4a48..34c1b7c23e 100644
--- a/usr/src/boot/lib/libstand/zfs/zfs.c
+++ b/usr/src/boot/lib/libstand/zfs/zfs.c
@@ -401,7 +401,7 @@ vdev_read(vdev_t *vdev __unused, void *priv, off_t offset, void *buf,
 		full_sec_size -= secsz;
 
 	/* Return of partial sector data requires a bounce buffer. */
-	if ((head > 0) || do_tail_read) {
+	if ((head > 0) || do_tail_read || bytes < secsz) {
 		bouncebuf = malloc(secsz);
 		if (bouncebuf == NULL) {
 			printf("vdev_read: out of memory\n");
@@ -427,12 +427,21 @@ vdev_read(vdev_t *vdev __unused, void *priv, off_t offset, void *buf,
 
 	/* Full data return from read sectors */
 	if (full_sec_size > 0) {
-		res = read(fd, outbuf, full_sec_size);
-		if (res != full_sec_size) {
-			ret = EIO;
-			goto error;
+		if (bytes < full_sec_size) {
+			res = read(fd, bouncebuf, secsz);
+			if (res != secsz) {
+				ret = EIO;
+				goto error;
+			}
+			memcpy(outbuf, bouncebuf, bytes);
+		} else {
+			res = read(fd, outbuf, full_sec_size);
+			if (res != full_sec_size) {
+				ret = EIO;
+				goto error;
+			}
+			outbuf += full_sec_size;
 		}
-		outbuf += full_sec_size;
 	}
 
 	/* Partial data return from last sector */