From: Kevin Wolf Date: Wed, 26 Mar 2014 13:06:04 +0100 Subject: [PATCH] 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 (cherry picked from commit 11b128f4062dd7f89b14abc8877ff20d41b28be9) Conflicts: tests/qemu-iotests/080 tests/qemu-iotests/080.out --- block/qcow2.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/block/qcow2.c b/block/qcow2.c index af0a45c..c9beb01 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -515,9 +515,6 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags) goto fail; } - s->snapshots_offset = header.snapshots_offset; - s->nb_snapshots = header.nb_snapshots; - /* read the level 1 table */ if (header.l1_size > 0x2000000) { /* 32 MB L1 table is enough for 2 PB images at 64k cluster size @@ -605,6 +602,10 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, 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;