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[Qemu-devel] [PULL 42/42] block: fix backing file segfault
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PULL 42/42] block: fix backing file segfault |
Date: |
Wed, 15 Jan 2014 11:22:55 +0100 |
From: Peter Feiner <address@hidden>
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 <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
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
- [Qemu-devel] [PULL 36/42] qapi: QMP interface for blkdebug and blkverify, (continued)
- [Qemu-devel] [PULL 37/42] qemu-io: Make filename optional, Kevin Wolf, 2014/01/15
- [Qemu-devel] [PULL 39/42] tests: Add test for qdict_flatten(), Kevin Wolf, 2014/01/15
- [Qemu-devel] [PULL 40/42] iotests: Test new blkdebug/blkverify interface, Kevin Wolf, 2014/01/15
- [Qemu-devel] [PULL 38/42] tests: Add test for qdict_array_split(), Kevin Wolf, 2014/01/15
- [Qemu-devel] [PULL 41/42] iotests: Test file format nesting, Kevin Wolf, 2014/01/15
- [Qemu-devel] [PULL 42/42] block: fix backing file segfault,
Kevin Wolf <=
- [Qemu-devel] [PULL 27/42] block: Allow block devices without files, Kevin Wolf, 2014/01/15