smb: client: fix potential deadlock when releasing mids

Vulnerability Description

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*

References

• https://git.kernel.org/stable/c/99f476e27aad5964ab13777d84fda67d1356dec1
• https://git.kernel.org/stable/c/ce49569079a9d4cad26c0f1d4653382fd9a5ca7a
• https://git.kernel.org/stable/c/9eb44db68c5b7f5aa22b8fc7de74a3e2e08d1f29
• https://git.kernel.org/stable/c/b9bb9607b1fc12fca51f5632da25b36975f599bf
• https://git.kernel.org/stable/c/c1a5962f1462b64fe7b69f20a4b6af8067bc2d26
• https://git.kernel.org/stable/c/e6322fd177c6885a21dd4609dc5e5c973d1a2eb7