[PATCH] md/raid10: fix null ptr dereference in raid10_size()

[Yu Kuai]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

In raid10_run() if raid10_set_queue_limits() succeed, the return value
is set to zero, and if following procedures failed raid10_run() will
return zero while mddev->private is still NULL, causing null ptr
dereference in raid10_size().

Fix the problem by only overwrite the return value if
raid10_set_queue_limits() failed.

Fixes: 3d8466ba68d4 ("md/raid10: use the atomic queue limit update APIs")
Reported-and-tested-by: ValdikSS <iam@xxxxxxxxxxxxxxx>
Closes: https://lore.kernel.org/all/0dd96820-fe52-4841-bc58-dbf14d6bfcc8@xxxxxxxxxxxxxxx/
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 drivers/md/raid10.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index f3bf1116794a..862b1fb71d86 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4061,9 +4061,12 @@ static int raid10_run(struct mddev *mddev)
 	}
 
 	if (!mddev_is_dm(conf->mddev)) {
-		ret = raid10_set_queue_limits(mddev);
-		if (ret)
+		int err = raid10_set_queue_limits(mddev);
+
+		if (err) {
+			ret = err;
 			goto out_free_conf;
+		}
 	}
 
 	/* need to check that every block has at least one working mirror */
-- 
2.39.2