cifs: fix GlobalMid_Lock bug in cifs_reconnect

commit 61cabc7b0a5cf0d3c532cfa96594c801743fe7f6 upstream.

We can not hold the GlobalMid_Lock spinlock during the
dfs processing in cifs_reconnect since it invokes things that may sleep
and thus trigger :

BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:23

Thus we need to drop the spinlock during this code block.

RHBZ: 1716743

Cc: stable@vger.kernel.org
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Acked-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 4c0e44489f21497670131b5a889ae6f4eb0b843e..e9507fba0b36941739f88eb421cc556b91cbf0fa 100644 (file)
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -478,6 +478,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
        spin_lock(&GlobalMid_Lock);
        server->nr_targets = 1;
 #ifdef CONFIG_CIFS_DFS_UPCALL
+       spin_unlock(&GlobalMid_Lock);
        cifs_sb = find_super_by_tcp(server);
        if (IS_ERR(cifs_sb)) {
                rc = PTR_ERR(cifs_sb);
@@ -495,6 +496,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
        }
        cifs_dbg(FYI, "%s: will retry %d target(s)\n", __func__,
                 server->nr_targets);
+       spin_lock(&GlobalMid_Lock);
 #endif
        if (server->tcpStatus == CifsExiting) {
                /* the demux thread will exit normally