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Re: [Qemu-devel] [PATCH for-2.0 10/47] bochs: Use unsigned variables for


From: Max Reitz
Subject: Re: [Qemu-devel] [PATCH for-2.0 10/47] bochs: Use unsigned variables for offsets and sizes (CVE-2014-0147)
Date: Wed, 26 Mar 2014 21:02:56 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0

On 26.03.2014 13:05, Stefan Hajnoczi wrote:
From: Kevin Wolf <address@hidden>

Gets us rid of integer overflows resulting in negative sizes which
aren't correctly checked.

Signed-off-by: Kevin Wolf <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
---
  block/bochs.c              | 16 ++++++++--------
  tests/qemu-iotests/078     |  8 ++++++++
  tests/qemu-iotests/078.out |  4 ++++
  3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/block/bochs.c b/block/bochs.c
index ef8e381..e923eed 100644
--- a/block/bochs.c
+++ b/block/bochs.c
@@ -67,13 +67,13 @@ struct bochs_header {
  typedef struct BDRVBochsState {
      CoMutex lock;
      uint32_t *catalog_bitmap;
-    int catalog_size;
+    uint32_t catalog_size;
- int data_offset;
+    uint32_t data_offset;
- int bitmap_blocks;
-    int extent_blocks;
-    int extent_size;
+    uint32_t bitmap_blocks;
+    uint32_t extent_blocks;
+    uint32_t extent_size;
  } BDRVBochsState;
static int bochs_probe(const uint8_t *buf, int buf_size, const char *filename)
@@ -97,7 +97,7 @@ static int bochs_open(BlockDriverState *bs, QDict *options, 
int flags,
                        Error **errp)
  {
      BDRVBochsState *s = bs->opaque;
-    int i;
+    uint32_t i;
      struct bochs_header bochs;
      int ret;
@@ -153,8 +153,8 @@ fail:
  static int64_t seek_to_sector(BlockDriverState *bs, int64_t sector_num)
  {
      BDRVBochsState *s = bs->opaque;
-    int64_t offset = sector_num * 512;
-    int64_t extent_index, extent_offset, bitmap_offset;
+    uint64_t offset = sector_num * 512;
+    uint64_t extent_index, extent_offset, bitmap_offset;
      char bitmap_entry;
// seek to sector
diff --git a/tests/qemu-iotests/078 b/tests/qemu-iotests/078
index f55f46d..73b573a 100755
--- a/tests/qemu-iotests/078
+++ b/tests/qemu-iotests/078
@@ -42,11 +42,19 @@ _supported_fmt bochs
  _supported_proto generic
  _supported_os Linux
+catalog_size_offset=$((0x48))
+
  echo
  echo "== Read from a valid image =="
  _use_sample_img empty.bochs.bz2
  { $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | 
_filter_testdir
+echo
+echo "== Negative catalog size =="
+_use_sample_img empty.bochs.bz2
+poke_file "$TEST_IMG" "$catalog_size_offset" "\xff\xff\xff\xff"
+{ $QEMU_IO -c "read 0 512" $TEST_IMG; } 2>&1 | _filter_qemu_io | 
_filter_testdir
+
  # success, all done
  echo "*** done"
  rm -f $seq.full
diff --git a/tests/qemu-iotests/078.out b/tests/qemu-iotests/078.out
index 25d37c5..ef8c42d 100644
--- a/tests/qemu-iotests/078.out
+++ b/tests/qemu-iotests/078.out
@@ -3,4 +3,8 @@ QA output created by 078
  == Read from a valid image ==
  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

This does not sound like the error message we'd like, but it is fixed by the next patch.

+no file open, try 'help open'
  *** done

Reviewed-by: Max Reitz <address@hidden>



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