linux-kernel - [PATCH 4.19 027/114] md: add mddev->pers to avoid potential NULL pointer dereference

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Date:   Thu, 23 May 2019 21:05:26 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Xiao Ni <xni@...hat.com>,
        NeilBrown <neilb@...e.com>, Yufen Yu <yuyufen@...wei.com>,
        Song Liu <songliubraving@...com>
Subject: [PATCH 4.19 027/114] md: add mddev->pers to avoid potential NULL pointer dereference

From: Yufen Yu <yuyufen@...wei.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@...hat.com>
Cc: NeilBrown <neilb@...e.com>
Cc: <stable@...r.kernel.org> # 4.4+
Reviewed-by: NeilBrown <neilb@...e.com>
Signed-off-by: Yufen Yu <yuyufen@...wei.com>
Signed-off-by: Song Liu <songliubraving@...com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2860,8 +2860,10 @@ 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