bochs: Check catalog_size header field (CVE-2014-0143)

It should neither become negative nor allow unbounded memory
allocations. This fixes aborts in g_malloc() and an s->catalog_bitmap
buffer overflow on big endian hosts.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

3 files changed, 35 insertions, 1 deletions

diff --git a/block/bochs.c b/block/bochs.c
index e923eedf3e..0ffa9c1ba7 100644
--- a/block/bochs.c
+++ b/block/bochs.c
@@ -123,7 +123,14 @@ static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
         bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
     }
 
+    /* Limit to 1M entries to avoid unbounded allocation. This is what is
+     * needed for the largest image that bximage can create (~8 TB). */
     s->catalog_size = le32_to_cpu(bochs.catalog);
+    if (s->catalog_size > 0x100000) {
+        error_setg(errp, "Catalog size is too large");
+        return -EFBIG;
+    }
+
     s->catalog_bitmap = g_malloc(s->catalog_size * 4);
 
     ret = bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_bitmap,
@@ -142,6 +149,12 @@ static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
 
     s->extent_size = le32_to_cpu(bochs.extent);
 
+    if (s->catalog_size < bs->total_sectors / s->extent_size) {
+        error_setg(errp, "Catalog size is too small for this disk size");
+        ret = -EINVAL;
+        goto fail;
+    }
+
     qemu_co_mutex_init(&s->lock);
     return 0;
 
diff --git a/tests/qemu-iotests/078 b/tests/qemu-iotests/078
index 73b573a624..902ef0f036 100755
--- a/tests/qemu-iotests/078
+++ b/tests/qemu-iotests/078
@@ -43,6 +43,7 @@ _supported_proto generic
 _supported_os Linux
 
 catalog_size_offset=$((0x48))
+disk_size_offset=$((0x58))
 
 echo
 echo "== Read from a valid image =="
@@ -55,6 +56,18 @@ _use_sample_img empty.bochs.bz2
 poke_file "$TEST_IMG" "$catalog_size_offset" "\xff\xff\xff\xff"
 { $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
 
+echo
+echo "== Overflow for catalog size * sizeof(uint32_t) =="
+_use_sample_img empty.bochs.bz2
+poke_file "$TEST_IMG" "$catalog_size_offset" "\x00\x00\x00\x40"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
+echo
+echo "== Too small catalog bitmap for image size =="
+_use_sample_img empty.bochs.bz2
+poke_file "$TEST_IMG" "$disk_size_offset" "\x00\xc0\x0f\x00\x00\x00\x00\x7f"
+{ $QEMU_IO -c "read 2T 4k" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
 # success, all done
 echo "*** done"
 rm -f $seq.full
diff --git a/tests/qemu-iotests/078.out b/tests/qemu-iotests/078.out
index ef8c42de9c..7254693b08 100644
--- a/tests/qemu-iotests/078.out
+++ b/tests/qemu-iotests/078.out
@@ -5,6 +5,14 @@ read 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 
 == Negative catalog size ==
-qemu-io: can't open device TEST_DIR/empty.bochs: Could not open 'TEST_DIR/empty.bochs': Interrupted system call
+qemu-io: can't open device TEST_DIR/empty.bochs: Catalog size is too large
+no file open, try 'help open'
+
+== Overflow for catalog size * sizeof(uint32_t) ==
+qemu-io: can't open device TEST_DIR/empty.bochs: Catalog size is too large
+no file open, try 'help open'
+
+== Too small catalog bitmap for image size ==
+qemu-io: can't open device TEST_DIR/empty.bochs: Catalog size is too small for this disk size
 no file open, try 'help open'
 *** done