fs/partitions/efi.c: corrupted GUID partition tables can cause kernel oops

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>

1 files changed, 9 insertions, 0 deletions

diff --git a/fs/partitions/efi.c b/fs/partitions/efi.c
index 19d6750d1d6c..6296b403c67a 100644
--- a/fs/partitions/efi.c
+++ b/fs/partitions/efi.c
@@ -310,6 +310,15 @@ static int is_gpt_valid(struct parsed_partitions *state, u64 lba,
                 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;