From 0471c6fe24a3bc1c12cf2dbf0efd7056a1f9fe0c Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@redhat.com>
Date: Thu, 19 Nov 2020 14:48:25 +0800
Subject: [PATCH] nbd: don't update block size after device is started

mainline inclusion
from mainline-v5.10-rc2
commit b40813ddcd6b
category: bugfix
bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1891363
CVE: NA
backport: openEuler-20.09

Here is the testcase:
1. rbd create --size 2G rbdpool/foo
2. rbd-nbd map rbdpool/foo
3. mkfs.ext4 /dev/nbd0
4. mount /dev/nbd0 /mnt
5. rbd resize --size 4G rbdpool/foo
6. ls /mnt
ls will stuck here forever.

--------------------------------

Mounted NBD device can be resized, one use case is rbd-nbd.

Fix the issue by setting up default block size, then not touch it
in nbd_size_update() any more. This kind of usage is aligned with loop
which has same use case too.

Cc: stable@vger.kernel.org
Fixes: c8a83a6b54d0 ("nbd: Use set_blocksize() to set device blocksize")
Reported-by: lining <lining2020x@163.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Jan Kara <jack@suse.cz>
Tested-by: lining <lining2020x@163.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: lining <lining_yewu@cmss.chinamobile.com>
Reviewed-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 drivers/block/nbd.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 8a4df4a9bca8..292129174c38 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -293,7 +293,7 @@ static void nbd_size_clear(struct nbd_device *nbd)
 	}
 }
 
-static void nbd_size_update(struct nbd_device *nbd)
+static void nbd_size_update(struct nbd_device *nbd, bool start)
 {
 	struct nbd_config *config = nbd->config;
 	struct block_device *bdev = bdget_disk(nbd->disk, 0);
@@ -309,7 +309,8 @@ static void nbd_size_update(struct nbd_device *nbd)
 	if (bdev) {
 		if (bdev->bd_disk) {
 			bd_set_size(bdev, config->bytesize);
-			set_blocksize(bdev, config->blksize);
+			if (start)
+				set_blocksize(bdev, config->blksize);
 		} else
 			bdev->bd_invalidated = 1;
 		bdput(bdev);
@@ -324,7 +325,7 @@ static void nbd_size_set(struct nbd_device *nbd, loff_t blocksize,
 	config->blksize = blocksize;
 	config->bytesize = blocksize * nr_blocks;
 	if (nbd->task_recv != NULL)
-		nbd_size_update(nbd);
+		nbd_size_update(nbd, false);
 }
 
 static void nbd_complete_rq(struct request *req)
@@ -1248,7 +1249,7 @@ static int nbd_start_device(struct nbd_device *nbd)
 		args->index = i;
 		queue_work(nbd->recv_workq, &args->work);
 	}
-	nbd_size_update(nbd);
+	nbd_size_update(nbd, true);
 	return error;
 }
 
-- 
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