smb: client: fix use-after-free of signing key

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: smb: client: fix use-after-free of signing key Customers have reported use-after-free in @ses->auth_key.response with SMB2.1 + sign mounts which occurs due to following race: task A task B cifs_mount() dfs_mount_share() get_session() cifs_mount_get_session() cifs_send_recv() cifs_get_smb_ses() compound_send_recv() cifs_setup_session() smb2_setup_request() kfree_sensitive() smb2_calc_signature() crypto_shash_setkey() *UAF* Fix this by ensuring that we have a valid @ses->auth_key.response by checking whether @ses->ses_status is SES_GOOD or SES_EXITING with @ses->ses_lock held. After commit 24a9799aa8ef ("smb: client: fix UAF in smb2_reconnect_server()"), we made sure to call ->logoff() only when @ses was known to be good (e.g. valid ->auth_key.response), so it's safe to access signing key when @ses->ses_status == SES_EXITING.

References

• https://git.kernel.org/stable/c/39619c65ab4bbb3e78c818f537687653e112764d
• https://git.kernel.org/stable/c/0e2b654a3848bf9da3b0d54c1ccf3f1b8c635591
• https://git.kernel.org/stable/c/343d7fe6df9e247671440a932b6a73af4fa86d95