[PATCH 4.4 15/29] cifs: initialize file_info_lock

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Rabin Vincent <rabinv@xxxxxxxx>

commit 81ddd8c0c5e1cb41184d66567140cb48c53eb3d1 upstream.

Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>

file_info_lock is not initalized in initiate_cifs_search(), leading to the
following splat after a simple "mount.cifs ... dir && ls dir/":

 BUG: spinlock bad magic on CPU#0, ls/486
  lock: 0xffff880009301110, .magic: 00000000, .owner: <none>/-1, .owner_cpu: 0
 CPU: 0 PID: 486 Comm: ls Not tainted 4.9.0 #27
 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996)
  ffffc900042f3db0 ffffffff81327533 0000000000000000 ffff880009301110
  ffffc900042f3dd0 ffffffff810baf75 ffff880009301110 ffffffff817ae077
  ffffc900042f3df0 ffffffff810baff6 ffff880009301110 ffff880008d69900
 Call Trace:
  [<ffffffff81327533>] dump_stack+0x65/0x92
  [<ffffffff810baf75>] spin_dump+0x85/0xe0
  [<ffffffff810baff6>] spin_bug+0x26/0x30
  [<ffffffff810bb159>] do_raw_spin_lock+0xe9/0x130
  [<ffffffff8159ad2f>] _raw_spin_lock+0x1f/0x30
  [<ffffffff8127e50d>] cifs_closedir+0x4d/0x100
  [<ffffffff81181cfd>] __fput+0x5d/0x160
  [<ffffffff81181e3e>] ____fput+0xe/0x10
  [<ffffffff8109410e>] task_work_run+0x7e/0xa0
  [<ffffffff81002512>] exit_to_usermode_loop+0x92/0xa0
  [<ffffffff810026f9>] syscall_return_slowpath+0x49/0x50
  [<ffffffff8159b484>] entry_SYSCALL_64_fastpath+0xa7/0xa9

Fixes: 3afca265b5f53a0 ("Clarify locking of cifs file and tcon structures and make more granular")
Signed-off-by: Rabin Vincent <rabinv@xxxxxxxx>
Signed-off-by: Steve French <smfrench@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 fs/cifs/readdir.c |    1 +
 1 file changed, 1 insertion(+)

--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -282,6 +282,7 @@ initiate_cifs_search(const unsigned int
 			rc = -ENOMEM;
 			goto error_exit;
 		}
+		spin_lock_init(&cifsFile->file_info_lock);
 		file->private_data = cifsFile;
 		cifsFile->tlink = cifs_get_tlink(tlink);
 		tcon = tlink_tcon(tlink);