libkmod-file: gracefully handle errors from zlib

zlib won't necessarily set the system errno, and this is particularly
evident on corrupted data (which results in a double free). Use zlib's
gzerror to detect the failure, returning a generic EINVAL when zlib
doesn't provide us with an errno.

diff --git a/libkmod/libkmod-file.c b/libkmod/libkmod-file.c
index 46ad8d9..8beb7e3 100644 (file)
--- a/libkmod/libkmod-file.c
+++ b/libkmod/libkmod-file.c
@@ -199,7 +199,13 @@ static int load_zlib(struct kmod_file *file)
                if (r == 0)
                        break;
                else if (r < 0) {
-                       err = -errno;
+                       int gzerr;
+                       const char *gz_errmsg = gzerror(file->gzf, &gzerr);
+
+                       ERR(file->ctx, "gzip: %s\n", gz_errmsg);
+
+                       /* gzip might not set errno here */
+                       err = gzerr == Z_ERRNO ? -errno : -EINVAL;
                        goto error;
                }
                did += r;