[Libguestfs] [nbdkit PATCH] offset: Better handling of parameters
The man page claims both offset and range are optional (matching the
code), but the --help text claims offset is mandatory, and the comment
to the no-op offset_config_complete claims we require both parameters.
We did not check for an offset larger than the underlying size when
there was no range, and even when there is a range, we were not
careful about integer overflow (offset=5E range=5E happily claims to
export a 5E image; but all bets are off if you later try to access
beyond the real underlying size). And in several cases, such as if
the plugin's get_size fails but range was not provided, we are not
returning -1 for failure.
Fixes: 3db69f56
Signed-off-by: Eric Blake <eblake(a)redhat.com>
---
The first post-1.14 bugfix. Too bad I didn't spot it earlier today.
filters/offset/offset.c | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)
diff --git a/filters/offset/offset.c b/filters/offset/offset.c
index 7df1ed13..1039a577 100644
--- a/filters/offset/offset.c
+++ b/filters/offset/offset.c
@@ -64,16 +64,9 @@ offset_config (nbdkit_next_config *next, void *nxdata,
return next (nxdata, key, value);
}
-/* Check the user did pass both parameters. */
-static int
-offset_config_complete (nbdkit_next_config_complete *next, void *nxdata)
-{
- return next (nxdata);
-}
-
#define offset_config_help \
- "offset=<OFFSET> (required) The start offset to serve.\n" \
- "range=<LENGTH> The total size to serve."
+ "offset=<OFFSET> The start offset to serve (default 0).\n"
\
+ "range=<LENGTH> The total size to serve (default rest of
file)."
/* Get the file size. */
static int64_t
@@ -82,16 +75,23 @@ offset_get_size (struct nbdkit_next_ops *next_ops, void *nxdata,
{
int64_t real_size = next_ops->get_size (nxdata);
+ if (real_size == -1)
+ return -1;
+
if (range >= 0) {
- if (offset + range > real_size) {
+ if (offset > real_size - range) {
nbdkit_error ("offset+range is larger than the real size "
"of the underlying file or device");
return -1;
}
return range;
}
- else
- return real_size - offset;
+ else if (offset > real_size) {
+ nbdkit_error ("offset is larger than the real size "
+ "of the underlying file or device");
+ return -1;
+ }
+ return real_size - offset;
}
/* Read data. */
@@ -176,7 +176,6 @@ static struct nbdkit_filter filter = {
.longname = "nbdkit offset filter",
.version = PACKAGE_VERSION,
.config = offset_config,
- .config_complete = offset_config_complete,
.config_help = offset_config_help,
.get_size = offset_get_size,
.pread = offset_pread,
--
2.21.0