Re: [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&gt; --- 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 _______________________________________________ Libguestfs mailing list Libguestfs(a)redhat.com https://www.redhat.com/mailman/listinfo/libguestfs