linux-kernel - [11/20] fs/partitions/efi.c: corrupted GUID partition tables can cause kernel oops

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Date:	Fri, 26 Aug 2011 15:03:34 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Timo Warns <warns@...-sense.de>,
	Matt Domsch <Matt_Domsch@...l.com>,
	Eugene Teo <eugeneteo@...nel.sg>,
	Dave Jones <davej@...emonkey.org.uk>
Subject: [11/20] fs/partitions/efi.c: corrupted GUID partition tables can cause kernel oops

2.6.33-longterm review patch.  If anyone has any objections, please let us know.

------------------

From: Timo Warns <Warns@...-sense.de>

commit 3eb8e74ec72736b9b9d728bad30484ec89c91dde upstream.

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.

[akpm@...ux-foundation.org: fix layout and indenting]
Signed-off-by: Timo Warns <warns@...-sense.de>
Cc: Matt Domsch <Matt_Domsch@...l.com>
Cc: Eugene Teo <eugeneteo@...nel.sg>
Cc: Dave Jones <davej@...emonkey.org.uk>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
[dannf: backported to Debian's 2.6.32]
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

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

--- a/fs/partitions/efi.c
+++ b/fs/partitions/efi.c
@@ -311,6 +311,15 @@ is_gpt_valid(struct block_device *bdev,
 		goto fail;
 	}

+	/* Check the GUID Partition Table header size */
+	if (le32_to_cpu((*gpt)->header_size) >
+			bdev_logical_block_size(bdev)) {
+		pr_debug("GUID Partition Table Header size is wrong: %u > %u\n",
+			le32_to_cpu((*gpt)->header_size),
+			bdev_logical_block_size(bdev));
+		goto fail;
+	}
+
 	/* Check the GUID Partition Table CRC */
 	origcrc = le32_to_cpu((*gpt)->header_crc32);
 	(*gpt)->header_crc32 = 0;

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