Re: [PATCH] partitions/efi: Fix integer overflow in GPT size calculation
From: Ard Biesheuvel <hidden>
Date: 2017-01-17 16:00:53
Also in:
linux-block, lkml
On 15 January 2017 at 22:31, Alden Tondettar [off-list ref] 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 <redacted>
Acked-by: Ard Biesheuvel <redacted>
quoted hunk ↗ jump to hunk
--- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html