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[Qemu-devel] [PATCH for-2.0 04/47] block/cloop: prevent offsets_size int
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH for-2.0 04/47] block/cloop: prevent offsets_size integer overflow (CVE-2014-0143) |
Date: |
Wed, 26 Mar 2014 13:05:26 +0100 |
The following integer overflow in offsets_size can lead to out-of-bounds
memory stores when n_blocks has a huge value:
uint32_t n_blocks, offsets_size;
[...]
ret = bdrv_pread(bs->file, 128 + 4, &s->n_blocks, 4);
[...]
s->n_blocks = be32_to_cpu(s->n_blocks);
/* read offsets */
offsets_size = s->n_blocks * sizeof(uint64_t);
s->offsets = g_malloc(offsets_size);
[...]
for(i=0;i<s->n_blocks;i++) {
s->offsets[i] = be64_to_cpu(s->offsets[i]);
offsets_size can be smaller than n_blocks due to integer overflow.
Therefore s->offsets[] is too small when the for loop byteswaps offsets.
This patch refuses to open files if offsets_size would overflow.
Note that changing the type of offsets_size is not a fix since 32-bit
hosts still only have 32-bit size_t.
Signed-off-by: Stefan Hajnoczi <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
block/cloop.c | 7 +++++++
tests/qemu-iotests/075 | 7 +++++++
tests/qemu-iotests/075.out | 4 ++++
3 files changed, 18 insertions(+)
diff --git a/block/cloop.c b/block/cloop.c
index f021663..563e916 100644
--- a/block/cloop.c
+++ b/block/cloop.c
@@ -99,6 +99,13 @@ static int cloop_open(BlockDriverState *bs, QDict *options,
int flags,
s->n_blocks = be32_to_cpu(s->n_blocks);
/* read offsets */
+ if (s->n_blocks > UINT32_MAX / sizeof(uint64_t)) {
+ /* Prevent integer overflow */
+ error_setg(errp, "n_blocks %u must be %zu or less",
+ s->n_blocks,
+ UINT32_MAX / sizeof(uint64_t));
+ return -EINVAL;
+ }
offsets_size = s->n_blocks * sizeof(uint64_t);
s->offsets = g_malloc(offsets_size);
diff --git a/tests/qemu-iotests/075 b/tests/qemu-iotests/075
index 8f54a99..9ce6b1f 100755
--- a/tests/qemu-iotests/075
+++ b/tests/qemu-iotests/075
@@ -43,6 +43,7 @@ _supported_proto generic
_supported_os Linux
block_size_offset=128
+n_blocks_offset=132
echo
echo "== check that the first sector can be read =="
@@ -67,6 +68,12 @@ _use_sample_img simple-pattern.cloop.bz2
poke_file "$TEST_IMG" "$block_size_offset" "\xff\xff\xfe\x00"
$QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
+echo
+echo "== offsets_size overflow ==="
+_use_sample_img simple-pattern.cloop.bz2
+poke_file "$TEST_IMG" "$n_blocks_offset" "\xff\xff\xff\xff"
+$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/075.out b/tests/qemu-iotests/075.out
index d362c95..a771789 100644
--- a/tests/qemu-iotests/075.out
+++ b/tests/qemu-iotests/075.out
@@ -15,4 +15,8 @@ no file open, try 'help open'
== huge block_size ===
qemu-io: can't open device TEST_DIR/simple-pattern.cloop: block_size
4294966784 must be 64 MB or less
no file open, try 'help open'
+
+== offsets_size overflow ===
+qemu-io: can't open device TEST_DIR/simple-pattern.cloop: n_blocks 4294967295
must be 536870911 or less
+no file open, try 'help open'
*** done
--
1.8.5.3
- [Qemu-devel] [PATCH for-2.0 00/47] block: image format input validation fixes, Stefan Hajnoczi, 2014/03/26
- [Qemu-devel] [PATCH for-2.0 02/47] qemu-iotests: add cloop input validation tests, Stefan Hajnoczi, 2014/03/26
- [Qemu-devel] [PATCH for-2.0 01/47] qemu-iotests: add ./check -cloop support, Stefan Hajnoczi, 2014/03/26
- [Qemu-devel] [PATCH for-2.0 03/47] block/cloop: validate block_size header field (CVE-2014-0144), Stefan Hajnoczi, 2014/03/26
- [Qemu-devel] [PATCH for-2.0 04/47] block/cloop: prevent offsets_size integer overflow (CVE-2014-0143),
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH for-2.0 05/47] block/cloop: refuse images with huge offsets arrays (CVE-2014-0144), Stefan Hajnoczi, 2014/03/26
- [Qemu-devel] [PATCH for-2.0 06/47] block/cloop: refuse images with bogus offsets (CVE-2014-0144), Stefan Hajnoczi, 2014/03/26
- [Qemu-devel] [PATCH for-2.0 08/47] qemu-iotests: Support for bochs format, Stefan Hajnoczi, 2014/03/26
- [Qemu-devel] [PATCH for-2.0 07/47] block/cloop: fix offsets[] size off-by-one, Stefan Hajnoczi, 2014/03/26
- [Qemu-devel] [PATCH for-2.0 09/47] bochs: Unify header structs and make them QEMU_PACKED, Stefan Hajnoczi, 2014/03/26