* [PATCH] partitions/efi: Fix integer overflow in GPT size calculation
@ 2017-01-15 22:31 Alden Tondettar
2017-01-17 16:00 ` Ard Biesheuvel
2017-01-17 16:03 ` Jens Axboe
0 siblings, 2 replies; 3+ messages in thread
From: Alden Tondettar @ 2017-01-15 22:31 UTC (permalink / raw)
To: Davidlohr Bueso, Jens Axboe, linux-efi, linux-block, linux-kernel
Cc: Alden Tondettar
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: Alden Tondettar <alden.tondettar@gmail.com>
---
block/partitions/efi.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/block/partitions/efi.c b/block/partitions/efi.c
index bcd86e5..39f70d9 100644
--- a/block/partitions/efi.c
+++ b/block/partitions/efi.c
@@ -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");
--
2.1.4
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] partitions/efi: Fix integer overflow in GPT size calculation
2017-01-15 22:31 [PATCH] partitions/efi: Fix integer overflow in GPT size calculation Alden Tondettar
@ 2017-01-17 16:00 ` Ard Biesheuvel
2017-01-17 16:03 ` Jens Axboe
1 sibling, 0 replies; 3+ messages in thread
From: Ard Biesheuvel @ 2017-01-17 16:00 UTC (permalink / raw)
To: Alden Tondettar
Cc: Davidlohr Bueso, Jens Axboe, linux-efi, linux-block, linux-kernel
On 15 January 2017 at 22:31, Alden Tondettar <alden.tondettar@gmail.com> wrote:
> 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: Alden Tondettar <alden.tondettar@gmail.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
> block/partitions/efi.c | 17 ++++++++++++-----
> 1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/block/partitions/efi.c b/block/partitions/efi.c
> index bcd86e5..39f70d9 100644
> --- a/block/partitions/efi.c
> +++ b/block/partitions/efi.c
> @@ -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");
> --
> 2.1.4
>
> --
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] partitions/efi: Fix integer overflow in GPT size calculation
2017-01-15 22:31 [PATCH] partitions/efi: Fix integer overflow in GPT size calculation Alden Tondettar
2017-01-17 16:00 ` Ard Biesheuvel
@ 2017-01-17 16:03 ` Jens Axboe
1 sibling, 0 replies; 3+ messages in thread
From: Jens Axboe @ 2017-01-17 16:03 UTC (permalink / raw)
To: Alden Tondettar, Davidlohr Bueso, linux-efi, linux-block, linux-kernel
On 01/15/2017 02:31 PM, Alden Tondettar wrote:
> 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.
Applied for 4.11, thanks.
--
Jens Axboe
^ permalink raw reply [flat|nested] 3+ messages in thread
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2017-01-15 22:31 [PATCH] partitions/efi: Fix integer overflow in GPT size calculation Alden Tondettar
2017-01-17 16:00 ` Ard Biesheuvel
2017-01-17 16:03 ` Jens Axboe
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