MD: Prevent sysfs operations on uninitialized kobjects

MD: Prevent sysfs operations on uninitialized kobjects

Device-mapper does not use sysfs; but when device-mapper is leveraging
MD's RAID personalities, MD sometimes attempts to update sysfs.  This
patch adds checks for 'mddev-kobj.sd' in sysfs_[un]link_rdev to ensure
it is about to operate on something valid.  This patch also checks for
'mddev->kobj.sd' before calling 'sysfs_notify' in 'remove_and_add_spares'.
Although 'sysfs_notify' already makes this check, doing so in
'remove_and_add_spares' prevents an additional mutex operation.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

2 files changed, 4 insertions, 6 deletions

diff --git a/drivers/md/md.c b/drivers/md/md.c
index fcb878f88796..aeceedfc530b 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -7663,10 +7663,8 @@ static int remove_and_add_spares(struct mddev *mddev)
                                 removed++;
                         }
                 }
-        if (removed)
-                sysfs_notify(&mddev->kobj, NULL,
-                             "degraded");
-
+        if (removed && mddev->kobj.sd)
+                sysfs_notify(&mddev->kobj, NULL, "degraded");
 
         rdev_for_each(rdev, mddev) {
                 if (rdev->raid_disk >= 0 &&
diff --git a/drivers/md/md.h b/drivers/md/md.h
index eca59c3074ef..d90fb1a879e1 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -506,7 +506,7 @@ static inline char * mdname (struct mddev * mddev)
 static inline int sysfs_link_rdev(struct mddev *mddev, struct md_rdev *rdev)
 {
         char nm[20];
-        if (!test_bit(Replacement, &rdev->flags)) {
+        if (!test_bit(Replacement, &rdev->flags) && mddev->kobj.sd) {
                 sprintf(nm, "rd%d", rdev->raid_disk);
                 return sysfs_create_link(&mddev->kobj, &rdev->kobj, nm);
         } else
@@ -516,7 +516,7 @@ static inline int sysfs_link_rdev(struct mddev *mddev, struct md_rdev *rdev)
 static inline void sysfs_unlink_rdev(struct mddev *mddev, struct md_rdev *rdev)
 {
         char nm[20];
-        if (!test_bit(Replacement, &rdev->flags)) {
+        if (!test_bit(Replacement, &rdev->flags) && mddev->kobj.sd) {
                 sprintf(nm, "rd%d", rdev->raid_disk);
                 sysfs_remove_link(&mddev->kobj, nm);
         }