Patch "nbd: fix uaf in nbd_open" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    nbd: fix uaf in nbd_open

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nbd-fix-uaf-in-nbd_open.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 77347a8505e3a84797ef1b8474922e2feefe48bf
Author: Li Lingfeng <lilingfeng3@xxxxxxxxxx>
Date:   Tue Nov 7 18:34:35 2023 +0800

    nbd: fix uaf in nbd_open
    
    [ Upstream commit 327462725b0f759f093788dfbcb2f1fd132f956b ]
    
    Commit 4af5f2e03013 ("nbd: use blk_mq_alloc_disk and
    blk_cleanup_disk") cleans up disk by blk_cleanup_disk() and it won't set
    disk->private_data as NULL as before. UAF may be triggered in nbd_open()
    if someone tries to open nbd device right after nbd_put() since nbd has
    been free in nbd_dev_remove().
    
    Fix this by implementing ->free_disk and free private data in it.
    
    Fixes: 4af5f2e03013 ("nbd: use blk_mq_alloc_disk and blk_cleanup_disk")
    Signed-off-by: Li Lingfeng <lilingfeng3@xxxxxxxxxx>
    Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20231107103435.2074904-1-lilingfeng@xxxxxxxxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 7718c81e1dba8..e94d2ff6b1223 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -250,7 +250,6 @@ static void nbd_dev_remove(struct nbd_device *nbd)
 	struct gendisk *disk = nbd->disk;
 
 	del_gendisk(disk);
-	put_disk(disk);
 	blk_mq_free_tag_set(&nbd->tag_set);
 
 	/*
@@ -261,7 +260,7 @@ static void nbd_dev_remove(struct nbd_device *nbd)
 	idr_remove(&nbd_index_idr, nbd->index);
 	mutex_unlock(&nbd_index_mutex);
 	destroy_workqueue(nbd->recv_workq);
-	kfree(nbd);
+	put_disk(disk);
 }
 
 static void nbd_dev_remove_work(struct work_struct *work)
@@ -1608,6 +1607,13 @@ static void nbd_release(struct gendisk *disk, fmode_t mode)
 	nbd_put(nbd);
 }
 
+static void nbd_free_disk(struct gendisk *disk)
+{
+	struct nbd_device *nbd = disk->private_data;
+
+	kfree(nbd);
+}
+
 static const struct block_device_operations nbd_fops =
 {
 	.owner =	THIS_MODULE,
@@ -1615,6 +1621,7 @@ static const struct block_device_operations nbd_fops =
 	.release =	nbd_release,
 	.ioctl =	nbd_ioctl,
 	.compat_ioctl =	nbd_ioctl,
+	.free_disk =	nbd_free_disk,
 };
 
 #if IS_ENABLED(CONFIG_DEBUG_FS)



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