From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48826) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WSteh-00062t-Of for qemu-devel@nongnu.org; Wed, 26 Mar 2014 15:38:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WSteb-0000fy-Nx for qemu-devel@nongnu.org; Wed, 26 Mar 2014 15:38:31 -0400 Message-ID: <53332CAB.5080507@redhat.com> Date: Wed, 26 Mar 2014 20:38:19 +0100 From: Max Reitz MIME-Version: 1.0 References: <1395835569-21193-1-git-send-email-stefanha@redhat.com> <1395835569-21193-4-git-send-email-stefanha@redhat.com> In-Reply-To: <1395835569-21193-4-git-send-email-stefanha@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH for-2.0 03/47] block/cloop: validate block_size header field (CVE-2014-0144) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi , qemu-devel@nongnu.org Cc: Kevin Wolf , pmatouse@redhat.com, qemu-stable@nongnu.org On 26.03.2014 13:05, Stefan Hajnoczi wrote: > 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 > Signed-off-by: Kevin Wolf > --- > block/cloop.c | 23 +++++++++++++++++++++++ > tests/qemu-iotests/075 | 20 ++++++++++++++++++++ > tests/qemu-iotests/075.out | 12 ++++++++++++ > 3 files changed, 55 insertions(+) > > diff --git a/block/cloop.c b/block/cloop.c > index b907023..f021663 100644 > --- a/block/cloop.c > +++ b/block/cloop.c > @@ -26,6 +26,9 @@ > #include "qemu/module.h" > #include > > +/* 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", Technically, this should be PRIu32. Also, the output looks kind of strange (as can be seen in the test output), but I can't think of any equally short way of expressing this. > + 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", Same here (for the first %u). > + s->block_size, > + MAX_BLOCK_SIZE / (1024 * 1024)); > + return -EINVAL; > + } > > ret = bdrv_pread(bs->file, 128 + 4, &s->n_blocks, 4); > if (ret < 0) { > diff --git a/tests/qemu-iotests/075 b/tests/qemu-iotests/075 > index 88ae8bb..8f54a99 100755 > --- a/tests/qemu-iotests/075 > +++ b/tests/qemu-iotests/075 > @@ -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 > diff --git a/tests/qemu-iotests/075.out b/tests/qemu-iotests/075.out > index 26661fa..d362c95 100644 > --- a/tests/qemu-iotests/075.out > +++ b/tests/qemu-iotests/075.out > @@ -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 Reviewed-by: Max Reitz