From 63090dac3a7c5fe02b4285cf2e5fb7017d2c7b0e Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 12 Apr 2012 14:01:03 +0200 Subject: [PATCH] block: open backing file as read-only when probing for size 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 Signed-off-by: Paolo Bonzini Signed-off-by: Kevin Wolf --- block.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/block.c b/block.c index dbd60e3f3e..754a422a63 100644 --- a/block.c +++ b/block.c @@ -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;