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From eeb629102da9a9a916d201bbd5f13ee7ad23844d Mon Sep 17 00:00:00 2001
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From: Karel Zak <kzak@redhat.com>
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Date: Tue, 22 Sep 2015 15:27:39 +0200
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Subject: [PATCH 110/116] libblkid: (zfs) keep bufferes read-only
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Upstream: https://github.com/karelzak/util-linux/commit/9325a8be9e55cc01d9f580e14dd2193829245183
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Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=1392661
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Signed-off-by: Karel Zak <kzak@redhat.com>
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---
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 libblkid/src/superblocks/zfs.c | 11 ++++++++---
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 1 file changed, 8 insertions(+), 3 deletions(-)
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diff --git a/libblkid/src/superblocks/zfs.c b/libblkid/src/superblocks/zfs.c
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index 9b5601e..8e88b39 100644
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--- a/libblkid/src/superblocks/zfs.c
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+++ b/libblkid/src/superblocks/zfs.c
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@@ -70,9 +70,10 @@ struct nvlist {
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 static void zfs_extract_guid_name(blkid_probe pr, loff_t offset)
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 {
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+	unsigned char *p, buff[4096];
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 	struct nvlist *nvl;
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 	struct nvpair *nvp;
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-	size_t left = 4096;
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+	size_t left = sizeof(buff);
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 	int found = 0;
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 	offset = (offset & ~(VDEV_LABEL_SIZE - 1)) + VDEV_LABEL_NVPAIR;
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@@ -81,10 +82,14 @@ static void zfs_extract_guid_name(blkid_probe pr, loff_t offset)
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 	 * the first 4k (left) of the nvlist.  This is true for all pools
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 	 * I've seen, and simplifies this code somewhat, because we don't
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 	 * have to handle an nvpair crossing a buffer boundary. */
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-	nvl = (struct nvlist *)blkid_probe_get_buffer(pr, offset, left);
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-	if (nvl == NULL)
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+	p = blkid_probe_get_buffer(pr, offset, left);
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+	if (!p)
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 		return;
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+	/* libblkid buffers are strictly readonly, but the code below modifies nvpair etc. */
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+	memcpy(buff, p, sizeof(buff));
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+	nvl = (struct nvlist *) buff;
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+
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 	nvdebug("zfs_extract: nvlist offset %llu\n", offset);
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 	nvp = &nvl->nvl_nvpair;
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-- 
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2.9.3
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