From eeb629102da9a9a916d201bbd5f13ee7ad23844d Mon Sep 17 00:00:00 2001
From: Karel Zak <kzak@redhat.com>
Date: Tue, 22 Sep 2015 15:27:39 +0200
Subject: [PATCH 110/116] libblkid: (zfs) keep bufferes read-only

Upstream: https://github.com/karelzak/util-linux/commit/9325a8be9e55cc01d9f580e14dd2193829245183
Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1392661
Signed-off-by: Karel Zak <kzak@redhat.com>
---
 libblkid/src/superblocks/zfs.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/libblkid/src/superblocks/zfs.c b/libblkid/src/superblocks/zfs.c
index 9b5601e..8e88b39 100644
--- a/libblkid/src/superblocks/zfs.c
+++ b/libblkid/src/superblocks/zfs.c
@@ -70,9 +70,10 @@ struct nvlist {

 static void zfs_extract_guid_name(blkid_probe pr, loff_t offset)
 {
+	unsigned char *p, buff[4096];
	struct nvlist *nvl;
	struct nvpair *nvp;
-	size_t left = 4096;
+	size_t left = sizeof(buff);
	int found = 0;

	offset = (offset & ~(VDEV_LABEL_SIZE - 1)) + VDEV_LABEL_NVPAIR;
@@ -81,10 +82,14 @@ static void zfs_extract_guid_name(blkid_probe pr, loff_t offset)
	 * the first 4k (left) of the nvlist.  This is true for all pools
	 * I've seen, and simplifies this code somewhat, because we don't
	 * have to handle an nvpair crossing a buffer boundary. */
-	nvl = (struct nvlist *)blkid_probe_get_buffer(pr, offset, left);
-	if (nvl == NULL)
+	p = blkid_probe_get_buffer(pr, offset, left);
+	if (!p)
		return;

+	/* libblkid buffers are strictly readonly, but the code below modifies nvpair etc. */
+	memcpy(buff, p, sizeof(buff));
+	nvl = (struct nvlist *) buff;
+
	nvdebug("zfs_extract: nvlist offset %llu\n", offset);

	nvp = &nvl->nvl_nvpair;
--
2.9.3
