[PATCH 4.9 12/53] md: add mddev->pers to avoid potential NULL pointer dereference

Greg Kroah-Hartman
2019-05-23T19:09:11Z

From: Yufen Yu <yuyufen@huawei.com>

commit ee37e62191a59d253fc916b9fc763deb777211e2 upstream.

When doing re-add, we need to ensure rdev->mddev->pers is not NULL,
which can avoid potential NULL pointer derefence in fallowing
add_bound_rdev().

Fixes: a6da4ef85cef ("md: re-add a failed disk")
Cc: Xiao Ni <xni@redhat.com>
Cc: NeilBrown <neilb@suse.com>
Cc: <stable@vger.kernel.org> # 4.4+
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/md.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2694,8 +2694,10 @@ state_store(struct md_rdev *rdev, const
err = 0;
}
} else if (cmd_match(buf, "re-add")) {
- if (test_bit(Faulty, &rdev->flags) && (rdev->raid_disk == -1) &&
- rdev->saved_raid_disk >= 0) {
+ if (!rdev->mddev->pers)
+ err = -EINVAL;
+ else if (test_bit(Faulty, &rdev->flags) && (rdev->raid_disk == -1) &&
+ rdev->saved_raid_disk >= 0) {
/* clear_bit is performed _after_ all the devices
* have their local Faulty bit cleared. If any writes
* happen in the meantime in the local node, they