linux-kernel - [PATCH] md/raid0: fix NULL pointer dereference in create_strip

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Message-Id: <20251116021816.107648-1-yukuai@fnnas.com>
Date: Sun, 16 Nov 2025 10:18:16 +0800
From: "Yu Kuai" <yukuai@...as.com>
To: <song@...nel.org>, <linux-raid@...r.kernel.org>, 
	<linux-kernel@...r.kernel.org>
Cc: <yukuai@...as.com>, <linan122@...wei.com>, <xni@...hat.com>, 
	<czhong@...hat.com>
Subject: [PATCH] md/raid0: fix NULL pointer dereference in create_strip_zones() for dm-raid

Commit 2107457e31fa ("md/raid0: Move queue limit setup before r0conf
initialization") dereference mddev->gendisk unconditionally, which is
NULL for dm-raid.

Fix this problem by reverting to old codes for dm-raid.

Fixes: 2107457e31fa ("md/raid0: Move queue limit setup before r0conf initialization")
Reported-and-tested-by: Changhui Zhong <czhong@...hat.com>
Closes: https://lore.kernel.org/all/CAGVVp+VqVnvGeneUoTbYvBv2cw6GwQRrR3B-iQ-_9rVfyumoKA@mail.gmail.com/
Signed-off-by: Yu Kuai <yukuai@...as.com>
---
 drivers/md/raid0.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index 47aee1b1d4d1..985c377356eb 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -68,7 +68,10 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
 	struct strip_zone *zone;
 	int cnt;
 	struct r0conf *conf = kzalloc(sizeof(*conf), GFP_KERNEL);
-	unsigned int blksize = queue_logical_block_size(mddev->gendisk->queue);
+	unsigned int blksize = 512;
+
+	if (!mddev_is_dm(mddev))
+		blksize = queue_logical_block_size(mddev->gendisk->queue);
 
 	*private_conf = ERR_PTR(-ENOMEM);
 	if (!conf)
@@ -84,6 +87,10 @@ static int create_strip_zones(struct mddev *mddev, struct r0conf **private_conf)
 		sector_div(sectors, mddev->chunk_sectors);
 		rdev1->sectors = sectors * mddev->chunk_sectors;
 
+		if (mddev_is_dm(mddev))
+			blksize = max(blksize, queue_logical_block_size(
+				      rdev1->bdev->bd_disk->queue));
+
 		rdev_for_each(rdev2, mddev) {
 			pr_debug("md/raid0:%s:   comparing %pg(%llu)"
 				 " with %pg(%llu)\n",
-- 
2.51.0