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Subject[10/19] fs/partitions/efi.c: corrupted GUID partition tables can cause kernel oops
2.6.32-longterm review patch.  If anyone has any objections, please let us know.

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

From: Timo Warns <Warns@pre-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@linux-foundation.org: fix layout and indenting]
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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[dannf: backported to Debian's 2.6.32]
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.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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