md: avoid dereferencing NULL pointer when accessing suspend_* sysfs attributes.

commit b8d966efd9a46a9a35beac50cbff6e30565125ef upstream.

If we try to modify one of the md/ sysfs files
  suspend_lo or suspend_hi
when the array is not active, we dereference a NULL.
Protect against that.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index ebbc3bb9a5cbf1276c1bc4fb4ba51737d56300b9..b60d328f6b1ead3a8ee3ba6275843785d9170ddd 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -3281,7 +3281,8 @@ suspend_lo_store(mddev_t *mddev, const char *buf, size_t len)
        char *e;
        unsigned long long new = simple_strtoull(buf, &e, 10);
 
-       if (mddev->pers->quiesce == NULL)
+       if (mddev->pers == NULL ||
+           mddev->pers->quiesce == NULL)
                return -EINVAL;
        if (buf == e || (*e && *e != '\n'))
                return -EINVAL;
@@ -3309,7 +3310,8 @@ suspend_hi_store(mddev_t *mddev, const char *buf, size_t len)
        char *e;
        unsigned long long new = simple_strtoull(buf, &e, 10);
 
-       if (mddev->pers->quiesce == NULL)
+       if (mddev->pers == NULL ||
+           mddev->pers->quiesce == NULL)
                return -EINVAL;
        if (buf == e || (*e && *e != '\n'))
                return -EINVAL;