On 15 January 2017 at 22:31, Alden Tondettar <[email protected]> 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 <[email protected]>
Acked-by: Ard Biesheuvel <[email protected]> > --- > 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 [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html
