On Thu, Jun 29, 2017 at 01:18:24PM +0200, Kevin Wolf wrote:
Am 29.06.2017 um 08:03 hat Manos Pitsidianakis geschrieben:bdrv_open_driver() is called in two places, bdrv_new_open_driver() and bdrv_open_common(). In the latter, failure cleanup in is in its caller, bdrv_open_inherit(), which unrefs the bs->file of the failed driver open if it exists. Let's check for this in bdrv_new_open_driver() as well.Signed-off-by: Manos Pitsidianakis <el13...@mail.ntua.gr> --- block.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/block.c b/block.c index 694396281b..aeacd520e0 100644 --- a/block.c +++ b/block.c @@ -1165,6 +1165,9 @@ BlockDriverState *bdrv_new_open_driver(BlockDriver *drv, const char *node_name, ret = bdrv_open_driver(bs, drv, node_name, bs->options, flags, errp); if (ret < 0) { + if (bs->file != NULL) { + bdrv_unref_child(bs, bs->file); + } QDECREF(bs->explicit_options); QDECREF(bs->options); bdrv_unref(bs);I think we should set bs->file = NULL here to remove the dangling pointer. I think it is never accessed anyway because of the bs->drv = NULL in the error path of bdrv_open_driver(), but better safe than sorry.
You can't see it in the diff but after bdrv_unref(bs), bdrv_new_open_driver returns NULL so there won't be any access to bs anyway. And since bs is destroyed by bdrv_unref (its refcount is 1), there's not really a point in setting bs->file = NULL.
But what would you think about avoiding the code duplication and just moving the bdrv_unref_child() call from bdrv_open_inherit() down to bdrv_open_driver(), so that bdrv_new_open_driver() is automatically covered?
The result would be the same, but this will cover future callers of bdrv_open_driver. Should I submit a v2?
And later we can maybe move it into the individual .bdrv_open implementations where it really belongs (whoever creates something is responsible for cleaning it up in error cases).
freeing bs->file was recently removed from individual '.bdrv_open's since bdrv_open_inherit takes care of it (de234897b60e034ba94b307fc289e2dc692c9251). I think this is simpler since a driver could neglect to free their bs->file whereas this is a catchall solution.
Kevin
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