In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix potential deadlock when releasing mids

All release_mid() callers seem to hold a reference of @mid so there is
no need to call kref_put(&mid->refcount, __release_mid) under
@server->mid_lock spinlock.  If they don't, then an use-after-free bug
would have occurred anyways.

By getting rid of such spinlock also fixes a potential deadlock as
shown below

CPU 0                                CPU 1
------------------------------------------------------------------
cifs_demultiplex_thread()            cifs_debug_data_proc_show()
 release_mid()
  spin_lock(&server->mid_lock);
                                     spin_lock(&cifs_tcp_ses_lock)
				      spin_lock(&server->mid_lock)
  __release_mid()
   smb2_find_smb_tcon()
    spin_lock(&cifs_tcp_ses_lock) *deadlock*

kernel.org https://git.kernel.org/stable/c/9eb44db68c5b7f5aa22b8fc7de74a3e2e08d1f29 [No types assigned]

kernel.org https://git.kernel.org/stable/c/b9bb9607b1fc12fca51f5632da25b36975f599bf [No types assigned]

kernel.org https://git.kernel.org/stable/c/c1a5962f1462b64fe7b69f20a4b6af8067bc2d26 [No types assigned]

kernel.org https://git.kernel.org/stable/c/e6322fd177c6885a21dd4609dc5e5c973d1a2eb7 [No types assigned]