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Commit c5082b70 authored by Alden Tondettar's avatar Alden Tondettar Committed by Jens Axboe
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partitions/efi: Fix integer overflow in GPT size calculation 



If a GUID Partition Table claims to have more than 2**25 entries, the
calculation of the partition table size in alloc_read_gpt_entries() will
overflow a 32-bit integer and not enough space will be allocated for the
table.

Nothing seems to get written out of bounds, but later efi_partition() will
read up to 32768 bytes from a 128 byte buffer, possibly OOPSing or exposing
information to /proc/partitions and uevents.

The problem exists on both 64-bit and 32-bit platforms.

Fix the overflow and also print a meaningful debug message if the table
size is too large.

Signed-off-by: default avatarAlden Tondettar <alden.tondettar@gmail.com>
Acked-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 1e668f4e

block/partitions/efi.c

+12 −5
Original line number Diff line number Diff line
@@ -293,7 +293,7 @@ static gpt_entry *alloc_read_gpt_entries(struct parsed_partitions *state, 
	if (!gpt)

		return NULL;



	count = le32_to_cpu(gpt->num_partition_entries) *

	count = (size_t)le32_to_cpu(gpt->num_partition_entries) *

                le32_to_cpu(gpt->sizeof_partition_entry);

	if (!count)

		return NULL;
@@ -352,7 +352,7 @@ static int is_gpt_valid(struct parsed_partitions *state, u64 lba, 
			gpt_header **gpt, gpt_entry **ptes)

{

	u32 crc, origcrc;

	u64 lastlba;

	u64 lastlba, pt_size;



	if (!ptes)

		return 0;
@@ -434,13 +434,20 @@ static int is_gpt_valid(struct parsed_partitions *state, u64 lba, 
		goto fail;

	}



	/* Sanity check partition table size */

	pt_size = (u64)le32_to_cpu((*gpt)->num_partition_entries) *

		le32_to_cpu((*gpt)->sizeof_partition_entry);

	if (pt_size > KMALLOC_MAX_SIZE) {

		pr_debug("GUID Partition Table is too large: %llu > %lu bytes\n",

			 (unsigned long long)pt_size, KMALLOC_MAX_SIZE);

		goto fail;

	}



	if (!(*ptes = alloc_read_gpt_entries(state, *gpt)))

		goto fail;



	/* Check the GUID Partition Entry Array CRC */

	crc = efi_crc32((const unsigned char *) (*ptes),

			le32_to_cpu((*gpt)->num_partition_entries) *

			le32_to_cpu((*gpt)->sizeof_partition_entry));

	crc = efi_crc32((const unsigned char *) (*ptes), pt_size);



	if (crc != le32_to_cpu((*gpt)->partition_entry_array_crc32)) {

		pr_debug("GUID Partition Entry Array CRC check failed.\n");