[Libguestfs] [nbdkit PATCH 1/5] xz: Avoid reading beyond EOF

Check that the file is long enough before reading the header, rather than violating assumptions of the backend that all requests have already passed bounds checks. Missed when converting from a plugin to a filter. Fixes: c879d310 Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- filters/xz/xzfile.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/filters/xz/xzfile.c b/filters/xz/xzfile.c index ee4af713..1ad010ef 100644 --- a/filters/xz/xzfile.c +++ b/filters/xz/xzfile.c @@ -117,6 +117,10 @@ check_header_magic (struct nbdkit_next_ops *next_ops, void *nxdata) char buf[XZ_HEADER_MAGIC_LEN]; int err; + if (next_ops->get_size (nxdata) < XZ_HEADER_MAGIC_LEN) { + nbdkit_error ("xz: file too short"); + return false; + } if (next_ops->pread (nxdata, buf, XZ_HEADER_MAGIC_LEN, 0, 0, &err) == -1) { nbdkit_error ("xz: could not read header magic: error %d", err); return false; -- 2.21.0