Don't corrupt 'supertype' when speculatively calling load_super1

When load_super1 is trying to see which sub-version of v1 superblock
is present, failure will cause it to clear st->ss, which is not good.

So use a temporary 'super_type' for the 'test if this version works'
calls, then copy that into 'st' on success.

diff --git a/super1.c b/super1.c
index cf46a2f33c5b7a71bf96102bacea9db19cc69550..52783e7766cf227ea26e99b85db2df59a34753ad 100644 (file)
--- a/super1.c
+++ b/super1.c
@@ -996,34 +996,35 @@ static int load_super1(struct supertype *st, int fd, void **sbp, char *devname)
 
        if (st->ss == NULL || st->minor_version == -1) {
                int bestvers = -1;
+               struct supertype tst;
                __u64 bestctime = 0;
                /* guess... choose latest ctime */
-               st->ss = &super1;
-               for (st->minor_version = 0; st->minor_version <= 2 ; st->minor_version++) {
+               tst.ss = &super1;
+               for (tst.minor_version = 0; tst.minor_version <= 2 ; tst.minor_version++) {
                        switch(load_super1(st, fd, sbp, devname)) {
                        case 0: super = *sbp;
                                if (bestvers == -1 ||
                                    bestctime < __le64_to_cpu(super->ctime)) {
-                                       bestvers = st->minor_version;
+                                       bestvers = tst.minor_version;
                                        bestctime = __le64_to_cpu(super->ctime);
                                }
                                free(super);
                                *sbp = NULL;
                                break;
-                       case 1: st->ss = NULL; return 1; /*bad device */
+                       case 1: return 1; /*bad device */
                        case 2: break; /* bad, try next */
                        }
                }
                if (bestvers != -1) {
                        int rv;
-                       st->minor_version = bestvers;
-                       st->ss = &super1;
-                       st->max_devs = 384;
+                       tst.minor_version = bestvers;
+                       tst.ss = &super1;
+                       tst.max_devs = 384;
                        rv = load_super1(st, fd, sbp, devname);
-                       if (rv) st->ss = NULL;
+                       if (rv == 0)
+                               *st = tst;
                        return rv;
                }
-               st->ss = NULL;
                return 2;
        }
        if (!get_dev_size(fd, devname, &dsize))