Patch "partitions/efi: Fix integer overflow in GPT size calculation" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

partitions/efi: Fix integer overflow in GPT size calculation

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
partitions-efi-fix-integer-overflow-in-gpt-size-calculation.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Alden Tondettar <[email protected]>
Date: Sun, 15 Jan 2017 15:31:56 -0700
Subject: partitions/efi: Fix integer overflow in GPT size calculation

From: Alden Tondettar <[email protected]>

[ 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.

---
 block/partitions/efi.c |   17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

@@ -293,7 +293,7 @@ static gpt_entry *alloc_read_gpt_entries
 	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_pa
 			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_pa
 		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 Partitition Entry Array CRC check failed.\n");

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/partitions-efi-fix-integer-overflow-in-gpt-size-calculation.patch