From: Kevin Wolf Date: Wed, 26 Mar 2014 13:05:43 +0100 Subject: [PATCH] qcow2: Check refcount table size (CVE-2014-0144) Limit the in-memory reference count table size to 8 MB, it's enough in practice. This fixes an unbounded allocation as well as a buffer overflow in qcow2_refcount_init(). Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz Signed-off-by: Stefan Hajnoczi (cherry picked from commit 5dab2faddc8eaa1fb1abdbe2f502001fc13a1b21) Conflicts: tests/qemu-iotests/080 tests/qemu-iotests/080.out --- block/qcow2-refcount.c | 4 +++- block/qcow2.c | 9 +++++++++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/block/qcow2-refcount.c b/block/qcow2-refcount.c index 1244693..cd641c9 100644 --- a/block/qcow2-refcount.c +++ b/block/qcow2-refcount.c @@ -38,8 +38,10 @@ static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs, int qcow2_refcount_init(BlockDriverState *bs) { BDRVQcowState *s = bs->opaque; - int ret, refcount_table_size2, i; + unsigned int refcount_table_size2, i; + int ret; + assert(s->refcount_table_size <= INT_MAX / sizeof(uint64_t)); refcount_table_size2 = s->refcount_table_size * sizeof(uint64_t); s->refcount_table = g_malloc(refcount_table_size2); if (s->refcount_table_size > 0) { diff --git a/block/qcow2.c b/block/qcow2.c index 4392111..884262b 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -455,10 +455,19 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags) s->csize_shift = (62 - (s->cluster_bits - 8)); s->csize_mask = (1 << (s->cluster_bits - 8)) - 1; s->cluster_offset_mask = (1LL << s->csize_shift) - 1; + s->refcount_table_offset = header.refcount_table_offset; s->refcount_table_size = header.refcount_table_clusters << (s->cluster_bits - 3); + if (header.refcount_table_clusters > (0x800000 >> s->cluster_bits)) { + /* 8 MB refcount table is enough for 2 PB images at 64k cluster size + * (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */ + fprintf(stderr, "Reference count table too large"); + ret = -EINVAL; + goto fail; + } + s->snapshots_offset = header.snapshots_offset; s->nb_snapshots = header.nb_snapshots;