[Qemu-devel] [PATCH 4/5] qcow1: Validate image size (CVE-2014-0223)

[Kevin Wolf <kwolf@redhat.com>]

A huge image size could cause s->l1_size to overflow. Make sure that
images never require a L1 table larger than what fits in s->l1_size.

This cannot only cause unbounded allocations, but also the allocation of
a too small L1 table, resulting in out-of-bounds array accesses (both
reads and writes).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/qcow.c               | 16 ++++++++++++++--
 tests/qemu-iotests/092     |  9 +++++++++
 tests/qemu-iotests/092.out |  7 +++++++
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/block/qcow.c b/block/qcow.c
index e8038e5..3566c05 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -61,7 +61,7 @@ typedef struct BDRVQcowState {
     int cluster_sectors;
     int l2_bits;
     int l2_size;
-    int l1_size;
+    unsigned int l1_size;
     uint64_t cluster_offset_mask;
     uint64_t l1_table_offset;
     uint64_t *l1_table;
@@ -166,7 +166,19 @@ static int qcow_open(BlockDriverState *bs, QDict *options, int flags,
 
     /* read the level 1 table */
     shift = s->cluster_bits + s->l2_bits;
-    s->l1_size = (header.size + (1LL << shift) - 1) >> shift;
+    if (header.size > UINT64_MAX - (1LL << shift)) {
+        error_setg(errp, "Image too large");
+        ret = -EINVAL;
+        goto fail;
+    } else {
+        uint64_t l1_size = (header.size + (1LL << shift) - 1) >> shift;
+        if (l1_size > INT_MAX / sizeof(uint64_t)) {
+            error_setg(errp, "Image too large");
+            ret = -EINVAL;
+            goto fail;
+        }
+        s->l1_size = l1_size;
+    }
 
     s->l1_table_offset = header.l1_table_offset;
     s->l1_table = g_malloc(s->l1_size * sizeof(uint64_t));
diff --git a/tests/qemu-iotests/092 b/tests/qemu-iotests/092
index 2196cce..26a1324 100755
--- a/tests/qemu-iotests/092
+++ b/tests/qemu-iotests/092
@@ -43,6 +43,7 @@ _supported_fmt qcow
 _supported_proto generic
 _supported_os Linux
 
+offset_size=24
 offset_cluster_bits=32
 offset_l2_bits=33
 
@@ -64,6 +65,14 @@ poke_file "$TEST_IMG" "$offset_l2_bits" "\xff"
 poke_file "$TEST_IMG" "$offset_l2_bits" "\x1b"
 { $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
 
+echo
+echo "== Invalid size =="
+_make_test_img 64M
+poke_file "$TEST_IMG" "$offset_size" "\xee\xee\xee\xee\xee\xee\xee\xee"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+poke_file "$TEST_IMG" "$offset_size" "\x7f\xff\xff\xff\xff\xff\xff\xff"
+{ $QEMU_IO -c "write 0 64M" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
 # success, all done
 echo "*** done"
 rm -f $seq.full
diff --git a/tests/qemu-iotests/092.out b/tests/qemu-iotests/092.out
index 45a7ac8..c3678a0 100644
--- a/tests/qemu-iotests/092.out
+++ b/tests/qemu-iotests/092.out
@@ -13,4 +13,11 @@ qemu-io: can't open device TEST_DIR/t.qcow: L2 table size must be between 512 an
 no file open, try 'help open'
 qemu-io: can't open device TEST_DIR/t.qcow: L2 table size must be between 512 and 64k
 no file open, try 'help open'
+
+== Invalid size ==
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 
+qemu-io: can't open device TEST_DIR/t.qcow: Image too large
+no file open, try 'help open'
+qemu-io: can't open device TEST_DIR/t.qcow: Image too large
+no file open, try 'help open'
 *** done
-- 
1.8.3.1