linux-kernel - [PATCH v2] partitions/efi: treat size mismatch as a warning, not an error

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Date:	Fri, 11 Oct 2013 08:47:34 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Karel Zak <kzak@...hat.com>,
	Matt Fleming <matt.fleming@...el.com>,
	Sean Paul <seanpaul@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Bill Richardson <wfrichar@...omium.org>,
	Josh Triplett <josh@...htriplett.org>,
	Doug Anderson <dianders@...omium.org>,
	Davidlohr Bueso <davidlohr@...com>
Subject: [PATCH v2] partitions/efi: treat size mismatch as a warning, not an error

In (27a7c64 partitions/efi: account for pmbr size in lba) we started
treating bad sizes in lba field of the partition that has the 0xEE
(GPT protective) as errors.  However, we may run into these "bad
sizes" in the real world if someone uses dd to copy an image from a
smaller disk to a bigger disk.  Since this case used to work (even
without using force_gpt), keep it working and treat the size mismatch
as a warning instead of an error.

Reported-by: Josh Triplett <josh@...htriplett.org>
Reported-by: Sean Paul <seanpaul@...omium.org>
Signed-off-by: Doug Anderson <dianders@...omium.org>
Reviewed-by: Josh Triplett <josh@...htriplett.org>
---
Changes in v2:
- Cleaned up comments/warning as per Davidlohr.

 block/partitions/efi.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/partitions/efi.c b/block/partitions/efi.c
index 1eb09ee..a8287b4 100644
--- a/block/partitions/efi.c
+++ b/block/partitions/efi.c
@@ -222,11 +222,16 @@ check_hybrid:
 	 * the disk size.
 	 *
 	 * Hybrid MBRs do not necessarily comply with this.
+	 *
+	 * Consider a bad value here to be a warning to support dd'ing
+	 * an image from a smaller disk to a larger disk.
 	 */
 	if (ret == GPT_MBR_PROTECTIVE) {
 		sz = le32_to_cpu(mbr->partition_record[part].size_in_lba);
 		if (sz != (uint32_t) total_sectors - 1 && sz != 0xFFFFFFFF)
-			ret = 0;
+			pr_debug("GPT: mbr size in lba (%u) different than whole disk (%u).\n",
+				 sz, min_t(uint32_t,
+					   total_sectors - 1, 0xFFFFFFFF));
 	}
 done:
 	return ret;
-- 
1.8.4

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