From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51983) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1W3Ndd-0008Ix-6Y for qemu-devel@nongnu.org; Wed, 15 Jan 2014 05:24:02 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1W3NdY-0000xs-9M for qemu-devel@nongnu.org; Wed, 15 Jan 2014 05:23:57 -0500 Received: from mx1.redhat.com ([209.132.183.28]:50039) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1W3NdX-0000xc-Qk for qemu-devel@nongnu.org; Wed, 15 Jan 2014 05:23:52 -0500 From: Kevin Wolf Date: Wed, 15 Jan 2014 11:22:55 +0100 Message-Id: <1389781375-11774-43-git-send-email-kwolf@redhat.com> In-Reply-To: <1389781375-11774-1-git-send-email-kwolf@redhat.com> References: <1389781375-11774-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PULL 42/42] block: fix backing file segfault List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: anthony@codemonkey.ws Cc: kwolf@redhat.com, qemu-devel@nongnu.org From: Peter Feiner When a backing file is opened such that (1) a protocol is directly used as the block driver and (2) the block driver has bdrv_file_open, bdrv_open_backing_file segfaults. The problem arises because bdrv_open_common returns without setting bd->backing_hd->file. To effect (1), you seem to have to use the -F flag in qemu-img. There are several block drivers that satisfy (2), such as "file" and "nbd". Here are some concrete examples: #!/bin/bash echo Test file format ./qemu-img create -f file base.file 1m ./qemu-img create -f qcow2 -F file -o backing_file=base.file\ file-overlay.qcow2 ./qemu-img convert -O raw file-overlay.qcow2 file-convert.raw echo Test nbd format SOCK=$PWD/nbd.sock ./qemu-img create -f raw base.raw 1m ./qemu-nbd -t -k $SOCK base.raw & trap "kill $!" EXIT while ! test -e $SOCK; do sleep 1; done ./qemu-img create -f qcow2 -F nbd -o backing_file=nbd:unix:$SOCK\ nbd-overlay.qcow2 ./qemu-img convert -O raw nbd-overlay.qcow2 nbd-convert.raw Without this patch, the two qemu-img convert commands segfault. This is a regression that was introduced in v1.7 by dbecebddfa4932d1c83915bcb9b5ba5984eb91be. Signed-off-by: Peter Feiner Reviewed-by: Max Reitz Signed-off-by: Kevin Wolf --- block.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/block.c b/block.c index 6af5f6e..418dbe9 100644 --- a/block.c +++ b/block.c @@ -1040,8 +1040,9 @@ int bdrv_open_backing_file(BlockDriverState *bs, QDict *options, Error **errp) error_free(local_err); return ret; } - pstrcpy(bs->backing_file, sizeof(bs->backing_file), - bs->backing_hd->file->filename); + if (bs->backing_hd->file) + pstrcpy(bs->backing_file, sizeof(bs->backing_file), + bs->backing_hd->file->filename); return 0; } -- 1.8.1.4