smb: client: fix potential UAF in cifs_dump_full_key()

Skip sessions that are being teared down (status == SES_EXITING) to
avoid UAF.

Cc: stable@vger.kernel.org
Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/client/ioctl.c b/fs/smb/client/ioctl.c
index c012dfdba80d457e27dc51996c55309840d3f892..855ac5a62edfaa50215cfed46e361dcb79f0c8fc 100644 (file)
--- a/fs/smb/client/ioctl.c
+++ b/fs/smb/client/ioctl.c
@@ -247,7 +247,9 @@ static int cifs_dump_full_key(struct cifs_tcon *tcon, struct smb3_full_key_debug
                spin_lock(&cifs_tcp_ses_lock);
                list_for_each_entry(server_it, &cifs_tcp_ses_list, tcp_ses_list) {
                        list_for_each_entry(ses_it, &server_it->smb_ses_list, smb_ses_list) {
-                               if (ses_it->Suid == out.session_id) {
+                               spin_lock(&ses_it->ses_lock);
+                               if (ses_it->ses_status != SES_EXITING &&
+                                   ses_it->Suid == out.session_id) {
                                        ses = ses_it;
                                        /*
                                         * since we are using the session outside the crit
@@ -255,9 +257,11 @@ static int cifs_dump_full_key(struct cifs_tcon *tcon, struct smb3_full_key_debug
                                         * so increment its refcount
                                         */
                                        cifs_smb_ses_inc_refcount(ses);
+                                       spin_unlock(&ses_it->ses_lock);
                                        found = true;
                                        goto search_end;
                                }
+                               spin_unlock(&ses_it->ses_lock);
                        }
                }
 search_end: