From: Timo Warns <Warns@pre-sense.de>
Subject: fs/partitions/efi.c: corrupted GUID partition tables can cause kernel oops
References: bnc#687113 CVE-2011-1577
Patch-mainline: Probably 2.6.39; In -mm already

The kernel automatically evaluates partition tables of storage devices.
The code for evaluating GUID partitions (in fs/partitions/efi.c) contains
a bug that causes a kernel oops on certain corrupted GUID partition
tables.

This bug has security impacts, because it allows, for example, to
prepare a storage device that crashes a kernel subsystem upon connecting
the device (e.g., a "USB Stick of (Partial) Death").

	crc = efi_crc32((const unsigned char *) (*gpt), le32_to_cpu((*gpt)->header_size));

computes a CRC32 checksum over gpt covering (*gpt)->header_size bytes. 
There is no validation of (*gpt)->header_size before the efi_crc32 call.

A corrupted partition table may have large values for (*gpt)->header_size.
 In this case, the CRC32 computation access memory beyond the memory
allocated for gpt, which may cause a kernel heap overflow.

Validate value of GUID partition table header size.

Signed-off-by: Timo Warns <warns@pre-sense.de>
Cc: Matt Domsch <Matt_Domsch@dell.com>
Cc: Eugene Teo <eugeneteo@kernel.sg>
Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Jeff Mahoney <jeffm@suse.com>
---

 fs/partitions/efi.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/fs/partitions/efi.c
+++ b/fs/partitions/efi.c
@@ -310,6 +310,15 @@ static int is_gpt_valid(struct parsed_pa
 		goto fail;
 	}
 
+	/* Check the GUID Partition Table header size */
+	if (le32_to_cpu((*gpt)->header_size) >
+			bdev_logical_block_size(state->bdev)) {
+		pr_debug("GUID Partition Table Header size is wrong: %u > %u\n",
+			le32_to_cpu((*gpt)->header_size),
+			bdev_logical_block_size(state->bdev));
+		goto fail;
+	}
+
 	/* Check the GUID Partition Table CRC */
 	origcrc = le32_to_cpu((*gpt)->header_crc32);
 	(*gpt)->header_crc32 = 0;
