super-ddf: Prevent crash when handling DDF metadata

A dummy function is defined because availability of ss->update_super is
not always verified.

This fix addresses a crash reported when assembling a RAID array using
mdadm with DDF metadata. For more details, see the discussion at:
https://lore.kernel.org/all/
CALHdMH30LuxR4tz9jP2ykDaDJtZ3P7L3LrZ+9e4Fq=Q6NwSM=Q@mail.gmail.com/

The discussion centers on an issue with mdadm where attempting to
assemble a RAID array caused a null pointer dereference. The problem
was traced to a missing update_super() function in super-ddf.c, which
led to a crash in Assemble.c.

Signed-off-by: lilinzhe <llz@antiy.cn>

diff --git a/super-ddf.c b/super-ddf.c
index 6cd099abe893a1ecf4b026fb95de60bdebdb8ffd..a06ed435bf4676379cbca64bead6b881e43923ad 100644 (file)
--- a/super-ddf.c
+++ b/super-ddf.c
@@ -5195,6 +5195,21 @@ static void default_geometry_ddf(struct supertype *st, int *level, int *layout,
                *layout = ddf_level_to_layout(*level);
 }
 
+static int update_super_ddf_dummy(struct supertype *st, struct mdinfo *info,
+                        enum update_opt update,
+                        char *devname, int verbose,
+                        int uuid_set, char *homehost)
+{
+       /*
+        * A dummy update_super function is required to ensure
+        * reliable handling of DDF metadata in mdadm.
+        * This implementation acts as a placeholder for cases
+        * where ss->update_super is not verified.
+        */
+       dprintf("update_super is not implemented in DDF\n");
+       return 0;
+}
+
 struct superswitch super_ddf = {
        .examine_super  = examine_super_ddf,
        .brief_examine_super = brief_examine_super_ddf,
@@ -5213,6 +5228,8 @@ struct superswitch super_ddf = {
        .uuid_from_super= uuid_from_super_ddf,
        .getinfo_super  = getinfo_super_ddf,
 
+       .update_super = update_super_ddf_dummy,
+
        .avail_size     = avail_size_ddf,
 
        .compare_super  = compare_super_ddf,