[PATCH][SMB3 client] fix potential deadlock in cifs_sync_mid_result

[Steve French <smfrench@xxxxxxxxx>]

Coverity spotted that the cifs_sync_mid_result function could deadlock

since cifs_server_dbg graps the srv_lock while we are still holding

the mid_lock

"Thread deadlock (ORDER_REVERSAL) lock_order: Calling spin_lock acquires
lock TCP_Server_Info.srv_lock while holding lock TCP_Server_Info.mid_lock"

Addresses-Coverity: 1590401 ("Thread deadlock (ORDER_REVERSAL)")

See attached patch

--

Thanks,

Steve

From 9b42329261067a500f2452f131c88c8cb0b62aa5 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@xxxxxxxxxxxxx>
Date: Tue, 23 Apr 2024 22:35:28 -0500
Subject: [PATCH] smb3: fix lock ordering potential deadlock in
 cifs_sync_mid_result

Coverity spotted that the cifs_sync_mid_result function could deadlock

"Thread deadlock (ORDER_REVERSAL) lock_order: Calling spin_lock acquires
lock TCP_Server_Info.srv_lock while holding lock TCP_Server_Info.mid_lock"

Addresses-Coverity: 1590401 ("Thread deadlock (ORDER_REVERSAL)")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
---
 fs/smb/client/transport.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/smb/client/transport.c b/fs/smb/client/transport.c
index 994d70193432..443b4b89431d 100644
--- a/fs/smb/client/transport.c
+++ b/fs/smb/client/transport.c
@@ -909,9 +909,11 @@ cifs_sync_mid_result(struct mid_q_entry *mid, struct TCP_Server_Info *server)
 			list_del_init(&mid->qhead);
 			mid->mid_flags |= MID_DELETED;
 		}
+		spin_unlock(&server->mid_lock);
 		cifs_server_dbg(VFS, "%s: invalid mid state mid=%llu state=%d\n",
 			 __func__, mid->mid, mid->mid_state);
-		rc = -EIO;
+		release_mid(mid);
+		return -EIO;
 	}
 	spin_unlock(&server->mid_lock);
 
-- 
2.40.1