Am 10.07.2017 um 15:29 hat Peter Lieven geschrieben:
> Am 10.07.2017 um 15:25 schrieb Kevin Wolf:
> >Am 29.06.2017 um 12:57 hat Peter Lieven geschrieben:
> >>we now read the extension on open and write it on update, but
> >>do not yet use it.
> >>
> >>Signed-off-by: Peter Lieven <p...@kamp.de>
> >>---
> >> block/qcow2.c | 100
> >> ++++++++++++++++++++++++++++++++++++++++++++++++++--------
> >> block/qcow2.h | 23 +++++++++++---
> >> 2 files changed, 104 insertions(+), 19 deletions(-)
> >>
> >>diff --git a/block/qcow2.c b/block/qcow2.c
> >>index 308121a..39a8afc 100644
> >>--- a/block/qcow2.c
> >>+++ b/block/qcow2.c
> >>@@ -63,6 +63,7 @@ typedef struct {
> >> #define QCOW2_EXT_MAGIC_END 0
> >> #define QCOW2_EXT_MAGIC_BACKING_FORMAT 0xE2792ACA
> >> #define QCOW2_EXT_MAGIC_FEATURE_TABLE 0x6803f857
> >>+#define QCOW2_EXT_MAGIC_COMPRESS_FORMAT 0xC03183A3
> >> static int qcow2_probe(const uint8_t *buf, int buf_size, const char
> >> *filename)
> >> {
> >>@@ -76,6 +77,26 @@ static int qcow2_probe(const uint8_t *buf, int buf_size,
> >>const char *filename)
> >> return 0;
> >> }
> >>+static int qcow2_compress_format_from_name(char *fmt)
> >>+{
> >>+ if (!fmt || !fmt[0]) {
> >>+ return QCOW2_COMPRESS_ZLIB_COMPAT;
> >>+ } else if (g_str_equal(fmt, "zlib")) {
> >>+ return QCOW2_COMPRESS_ZLIB;
> >>+ } else {
> >>+ return -EINVAL;
> >>+ }
> >>+}
> >It might make sense to allow specifying the old compression format in
> >the compression header. But I'm not so sure about using the empty string
> >rather than a proper name for it, and even less about not documenting
> >it.
>
> The old format is used if and only if the compression header is absent.
> It makes no sense to write a header and use the old format. The old
> settings are suboptimal and old versions can't open a qcow2 with a
> compression header anyway.
Your code allows an empty string in the header extension. If you don't
want it there, you need to reject it.
Kevin
