[PATCH] nbd: reclassify socket lock in nbd_reconnect_socket

[PATCH] nbd: reclassify socket lock in nbd_reconnect_socket

[Yun Zhou]

nbd_reconnect_socket() obtains a new socket via nbd_get_socket() but
does not call nbd_reclassify_socket(), leaving the socket's sk_lock in
the default AF_INET6 lockdep class.  This causes false circular lock
dependency warnings because lockdep merges the NBD socket's sk_lock
with unrelated sockets (e.g., rawv6_sendmsg) that establish a
sk_lock -> fs_reclaim dependency in normal operation.

nbd_add_socket() already reclassifies correctly on the initial connect
path, but the reconnect path was missed.

Add the missing nbd_reclassify_socket() call after nbd_get_socket() in
nbd_reconnect_socket().

Reported-by: syzbot+576095eed5658cbd9b63@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=576095eed5658cbd9b63
Fixes: d532cddb6c60 ("nbd: Reclassify sockets to avoid lockdep circular dependency")
Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
---
 drivers/block/nbd.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 8c6028e71e83..70a04d541ea4 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -1386,6 +1386,8 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
 	if (!sock)
 		return err;
 
+	nbd_reclassify_socket(sock);
+
 	args = kzalloc_obj(*args);
 	if (!args) {
 		sockfd_put(sock);
-- 
2.43.0

Re: [PATCH] nbd: reclassify socket lock in nbd_reconnect_socket

[Zhou, Yun]

Friendly ping.

On 7/6/2026 11:57 PM, Yun Zhou wrote:
> nbd_reconnect_socket() obtains a new socket via nbd_get_socket() but
> does not call nbd_reclassify_socket(), leaving the socket's sk_lock in
> the default AF_INET6 lockdep class.  This causes false circular lock
> dependency warnings because lockdep merges the NBD socket's sk_lock
> with unrelated sockets (e.g., rawv6_sendmsg) that establish a
> sk_lock -> fs_reclaim dependency in normal operation.
> 
> nbd_add_socket() already reclassifies correctly on the initial connect
> path, but the reconnect path was missed.
> 
> Add the missing nbd_reclassify_socket() call after nbd_get_socket() in
> nbd_reconnect_socket().
> 
> Reported-by: syzbot+576095eed5658cbd9b63@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=576095eed5658cbd9b63
> Fixes: d532cddb6c60 ("nbd: Reclassify sockets to avoid lockdep circular dependency")
> Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
> ---
>   drivers/block/nbd.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> index 8c6028e71e83..70a04d541ea4 100644
> --- a/drivers/block/nbd.c
> +++ b/drivers/block/nbd.c
> @@ -1386,6 +1386,8 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
>   	if (!sock)
>   		return err;
>   
> +	nbd_reclassify_socket(sock);
> +
>   	args = kzalloc_obj(*args);
>   	if (!args) {
>   		sockfd_put(sock);