bochs: Check extent_size header field (CVE-2014-0142)

This fixes two possible division by zero crashes: In bochs_open() and in
seek_to_sector().

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>

diff --git a/block/bochs.c b/block/bochs.c
index 0ffa9c1ba77c37d9d48b8691ed7533d47f30dc7c..a922782c1d47f7e63c167b6bad654bd2d8d09153 100644 (file)
--- a/block/bochs.c
+++ b/block/bochs.c
@@ -148,6 +148,14 @@ static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
     s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;
 
     s->extent_size = le32_to_cpu(bochs.extent);
+    if (s->extent_size == 0) {
+        error_setg(errp, "Extent size may not be zero");
+        return -EINVAL;
+    } else if (s->extent_size > 0x800000) {
+        error_setg(errp, "Extent size %" PRIu32 " is too large",
+                   s->extent_size);
+        return -EINVAL;
+    }
 
     if (s->catalog_size < bs->total_sectors / s->extent_size) {
         error_setg(errp, "Catalog size is too small for this disk size");

diff --git a/tests/qemu-iotests/078 b/tests/qemu-iotests/078
index 902ef0f03693adede63de350a91274430ea83b85..872e734cab835b9c03757ae463f238dbe63fc7bb 100755 (executable)
--- a/tests/qemu-iotests/078
+++ b/tests/qemu-iotests/078
@@ -43,6 +43,7 @@ _supported_proto generic
 _supported_os Linux
 
 catalog_size_offset=$((0x48))
+extent_size_offset=$((0x50))
 disk_size_offset=$((0x58))
 
 echo
@@ -68,6 +69,18 @@ _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
 
+echo
+echo "== Negative extent size =="
+_use_sample_img empty.bochs.bz2
+poke_file "$TEST_IMG" "$extent_size_offset" "\xff\xff\xff\xff"
+{ $QEMU_IO -c "read 768k 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | _filter_testdir
+
+echo
+echo "== Zero extent size =="
+_use_sample_img empty.bochs.bz2
+poke_file "$TEST_IMG" "$extent_size_offset" "\x00\x00\x00\x00"
+{ $QEMU_IO -c "read 0 512" $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 7254693b08bd823813545424d72096f228c97427..ea95ffdbb854fe57f6e891bc42639132e32b2585 100644 (file)
--- a/tests/qemu-iotests/078.out
+++ b/tests/qemu-iotests/078.out
@@ -15,4 +15,12 @@ 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'
+
+== Negative extent size ==
+qemu-io: can't open device TEST_DIR/empty.bochs: Extent size 4294967295 is too large
+no file open, try 'help open'
+
+== Zero extent size ==
+qemu-io: can't open device TEST_DIR/empty.bochs: Extent size may not be zero
+no file open, try 'help open'
 *** done