lkml.org 
[lkml]   [2017]   [Sep]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH for 4.9 45/59] partitions/efi: Fix integer overflow in GPT size calculation
Date
From: Alden Tondettar <alden.tondettar@gmail.com>

[ Upstream commit c5082b70adfe8e1ea1cf4a8eff92c9f260e364d2 ]

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>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.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 bcd86e5cd546..39f70d968754 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");
--
2.11.0
\
 
 \ /
  Last update: 2017-09-14 19:29    [W:0.391 / U:6.804 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site