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From 42eb58179b3b215bb507da3262b682b8a2ec10b5 Mon Sep 17 00:00:00 2001
From: Kevin Wolf <kwolf@redhat.com>
Date: Thu, 15 May 2014 16:10:11 +0200
Subject: [PATCH] qcow1: Validate L2 table size (CVE-2014-0222)
Too large L2 table sizes cause unbounded allocations. Images actually
created by qemu-img only have 512 byte or 4k L2 tables.
To keep things consistent with cluster sizes, allow ranges between 512
bytes and 64k (in fact, down to 1 entry = 8 bytes is technically
working, but L2 table sizes smaller than a cluster don't make a lot of
sense).
This also means that the number of bytes on the virtual disk that are
described by the same L2 table is limited to at most 8k * 64k or 2^29,
preventively avoiding any integer overflows.
Cc: qemu-stable@nongnu.org
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
---
block/qcow.c | 8 ++++++++
tests/qemu-iotests/092 | 15 +++++++++++++++
tests/qemu-iotests/092.out | 11 +++++++++++
3 files changed, 34 insertions(+)
diff --git a/block/qcow.c b/block/qcow.c
index e60df23..e8038e5 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -139,6 +139,14 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
goto fail;
}
+ /* l2_bits specifies number of entries; storing a uint64_t in each entry,
+ * so bytes = num_entries << 3. */
+ if (header.l2_bits < 9 - 3 || header.l2_bits > 16 - 3) {
+ error_setg(errp, "L2 table size must be between 512 and 64k");
+ ret = -EINVAL;
+ goto fail;
+ }
+
if (header.crypt_method > QCOW_CRYPT_AES) {
error_setg(errp, "invalid encryption method in qcow header");
ret = -EINVAL;
--
1.9.3