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authorPeter Feiner <peter@gridcentric.ca>2014-01-08 19:43:25 +0000
committerKevin Wolf <kwolf@redhat.com>2014-01-22 13:47:52 +0100
commitd80ac658f2caacfb14ea386211c4a9bea0cea280 (patch)
treec2eea663d2e7f9e7173cbe880c0064475a3c7858 /block.c
parent91f84f652de14329d5ad0666499a78fd0db0f1c7 (diff)
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block: fix backing file segfault
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 <peter@gridcentric.ca> Reviewed-by: Max Reitz <mreitz@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/block.c b/block.c
index 6af5f6e..53cc9e0 100644
--- a/block.c
+++ b/block.c
@@ -1040,8 +1040,12 @@ 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;
}