From: Kevin Wolf Date: Thu, 5 Mar 2015 10:42:00 +0000 (+0000) Subject: qcow2: Fix NULL dereference in qcow2_open() error path (CVE-2014-0146) X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=8c58457e2e407d3b674bbf0df61f75f6fcad4aee;p=qemu-upstream-4.3-testing.git qcow2: Fix NULL dereference in qcow2_open() error path (CVE-2014-0146) The qcow2 code assumes that s->snapshots is non-NULL if s->nb_snapshots != 0. By having the initialisation of both fields separated in qcow2_open(), any error occuring in between would cause the error path to dereference NULL in qcow2_free_snapshots() if the image had any snapshots. Signed-off-by: Kevin Wolf Reviewed-by: Max Reitz Signed-off-by: Stefan Hajnoczi Signed-off-by: Stefano Stabellini --- diff --git a/block/qcow2.c b/block/qcow2.c index c1ff31f48..e40f733f0 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -403,9 +403,6 @@ static int qcow2_open(BlockDriverState *bs, int flags) s->refcount_table_size = header.refcount_table_clusters << (s->cluster_bits - 3); - s->snapshots_offset = header.snapshots_offset; - s->nb_snapshots = header.nb_snapshots; - /* read the level 1 table */ s->l1_size = header.l1_size; s->l1_vm_state_index = size_to_l1(s, header.size); @@ -467,6 +464,10 @@ static int qcow2_open(BlockDriverState *bs, int flags) bs->backing_file[len] = '\0'; } + /* Internal snapshots */ + s->snapshots_offset = header.snapshots_offset; + s->nb_snapshots = header.nb_snapshots; + ret = qcow2_read_snapshots(bs); if (ret < 0) { goto fail;