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block: open backing file as read-only when probing for size

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bdrv_img_create will temporarily open the backing file to probe its size.
However, this could be done with a read-write open if the wrong flags are
passed to bdrv_img_create.  Since there is really no documentation on
what flags can be passed, assume that bdrv_img_create receives the flags
with which the new image will be opened; sanitize them when opening
the backing file.

Reported-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2012-04-12 14:01:03 +02:00 committed by Kevin Wolf
parent 469ef350e1
commit 63090dac3a
1 changed files with 6 additions and 1 deletions
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7
block.c
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@ -4103,10 +4103,15 @@ int bdrv_img_create(const char *filename, const char *fmt,
if (backing_file && backing_file->value.s) {
uint64_t size;
char buf[32];
int back_flags;
/* backing files always opened read-only */
back_flags =
flags & ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
bs = bdrv_new("");
ret = bdrv_open(bs, backing_file->value.s, flags, backing_drv);
ret = bdrv_open(bs, backing_file->value.s, back_flags, backing_drv);
if (ret < 0) {
error_report("Could not open '%s'", backing_file->value.s);
goto out;