smb: client: fix potential UAF in is_valid_oplock_break()

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/misc.c b/fs/smb/client/misc.c
index 1ea22b3955a2f46ea95caae43f921af2161cef2e..33ac4f8f5050c416cd2004ee4516756edd3b11d8 100644 (file)
--- a/fs/smb/client/misc.c
+++ b/fs/smb/client/misc.c
@@ -481,6 +481,8 @@ is_valid_oplock_break(char *buffer, struct TCP_Server_Info *srv)
        /* look up tcon based on tid & uid */
        spin_lock(&cifs_tcp_ses_lock);
        list_for_each_entry(ses, &pserver->smb_ses_list, smb_ses_list) {
+               if (cifs_ses_exiting(ses))
+                       continue;
                list_for_each_entry(tcon, &ses->tcon_list, tcon_list) {
                        if (tcon->tid != buf->Tid)
                                continue;