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block/cloop: validate block_size header field (CVE-2014-0144)

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Avoid unbounded s->uncompressed_block memory allocation by checking that
the block_size header field has a reasonable value.  Also enforce the
assumption that the value is a non-zero multiple of 512.

These constraints conform to cloop 2.639's code so we accept existing
image files.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2014-03-26 13:05:25 +01:00
parent 05560fcebb
commit d65f97a82c
3 changed files with 55 additions and 0 deletions
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23
block/cloop.c
View File

@ -26,6 +26,9 @@
#include "qemu/module.h"
#include <zlib.h>
/* Maximum compressed block size */
#define MAX_BLOCK_SIZE (64 * 1024 * 1024)
typedef struct BDRVCloopState {
CoMutex lock;
uint32_t block_size;
@ -68,6 +71,26 @@ static int cloop_open(BlockDriverState *bs, QDict *options, int flags,
return ret;
}
s->block_size = be32_to_cpu(s->block_size);
if (s->block_size % 512) {
error_setg(errp, "block_size %u must be a multiple of 512",
s->block_size);
return -EINVAL;
}
if (s->block_size == 0) {
error_setg(errp, "block_size cannot be zero");
return -EINVAL;
}
/* cloop's create_compressed_fs.c warns about block sizes beyond 256 KB but
* we can accept more. Prevent ridiculous values like 4 GB - 1 since we
* need a buffer this big.
*/
if (s->block_size > MAX_BLOCK_SIZE) {
error_setg(errp, "block_size %u must be %u MB or less",
s->block_size,
MAX_BLOCK_SIZE / (1024 * 1024));
return -EINVAL;
}
ret = bdrv_pread(bs->file, 128 + 4, &s->n_blocks, 4);
if (ret < 0) {

20
tests/qemu-iotests/075
View File

@ -42,11 +42,31 @@ _supported_fmt cloop
_supported_proto generic
_supported_os Linux
block_size_offset=128
echo
echo "== check that the first sector can be read =="
_use_sample_img simple-pattern.cloop.bz2
$QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
echo
echo "== block_size must be a multiple of 512 =="
_use_sample_img simple-pattern.cloop.bz2
poke_file "$TEST_IMG" "$block_size_offset" "\x00\x00\x02\x01"
$QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
echo
echo "== block_size cannot be zero =="
_use_sample_img simple-pattern.cloop.bz2
poke_file "$TEST_IMG" "$block_size_offset" "\x00\x00\x00\x00"
$QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
echo
echo "== huge block_size ==="
_use_sample_img simple-pattern.cloop.bz2
poke_file "$TEST_IMG" "$block_size_offset" "\xff\xff\xfe\x00"
$QEMU_IO -c "read 0 512" $TEST_IMG 2>&1 | _filter_qemu_io | _filter_testdir
# success, all done
echo "*** done"
rm -f $seq.full

12
tests/qemu-iotests/075.out
View File

@ -3,4 +3,16 @@ QA output created by 075
== check that the first sector can be read ==
read 512/512 bytes at offset 0
512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
== block_size must be a multiple of 512 ==
qemu-io: can't open device TEST_DIR/simple-pattern.cloop: block_size 513 must be a multiple of 512
no file open, try 'help open'
== block_size cannot be zero ==
qemu-io: can't open device TEST_DIR/simple-pattern.cloop: block_size cannot be zero
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'
*** done