From 5fa65527bc559920139e4cac72734b588fc9e432 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Tue, 20 Nov 2018 15:16:36 -0200 Subject: [PATCH] cifs: Always resolve hostname before reconnecting BugLink: https://bugs.launchpad.net/bugs/1837664 commit 28eb24ff75c5ac130eb326b3b4d0dcecfc0f427d upstream. In case a hostname resolves to a different IP address (e.g. long running mounts), make sure to resolve it every time prior to calling generic_ip_connect() in reconnect. Suggested-by: Steve French Signed-off-by: Paulo Alcantara Signed-off-by: Steve French Signed-off-by: Pavel Shilovsky Signed-off-by: Greg Kroah-Hartman Signed-off-by: Andrea Righi Signed-off-by: Khalid Elmously --- fs/cifs/connect.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+) diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index fc354fd578df..582996fd7e3b 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -51,6 +51,7 @@ #include "cifs_unicode.h" #include "cifs_debug.h" #include "cifs_fs_sb.h" +#include "dns_resolve.h" #include "ntlmssp.h" #include "nterr.h" #include "rfc1002pdu.h" @@ -313,6 +314,53 @@ static void cifs_prune_tlinks(struct work_struct *work); static int cifs_setup_volume_info(struct smb_vol *volume_info, char *mount_data, const char *devname); +/* + * Resolve hostname and set ip addr in tcp ses. Useful for hostnames that may + * get their ip addresses changed at some point. + * + * This should be called with server->srv_mutex held. + */ +#ifdef CONFIG_CIFS_DFS_UPCALL +static int reconn_set_ipaddr(struct TCP_Server_Info *server) +{ + int rc; + int len; + char *unc, *ipaddr = NULL; + + if (!server->hostname) + return -EINVAL; + + len = strlen(server->hostname) + 3; + + unc = kmalloc(len, GFP_KERNEL); + if (!unc) { + cifs_dbg(FYI, "%s: failed to create UNC path\n", __func__); + return -ENOMEM; + } + snprintf(unc, len, "\\\\%s", server->hostname); + + rc = dns_resolve_server_name_to_ip(unc, &ipaddr); + kfree(unc); + + if (rc < 0) { + cifs_dbg(FYI, "%s: failed to resolve server part of %s to IP: %d\n", + __func__, server->hostname, rc); + return rc; + } + + rc = cifs_convert_address((struct sockaddr *)&server->dstaddr, ipaddr, + strlen(ipaddr)); + kfree(ipaddr); + + return !rc ? -1 : 0; +} +#else +static inline int reconn_set_ipaddr(struct TCP_Server_Info *server) +{ + return 0; +} +#endif + /* * cifs tcp session reconnection * @@ -409,6 +457,11 @@ cifs_reconnect(struct TCP_Server_Info *server) rc = generic_ip_connect(server); if (rc) { cifs_dbg(FYI, "reconnect error %d\n", rc); + rc = reconn_set_ipaddr(server); + if (rc) { + cifs_dbg(FYI, "%s: failed to resolve hostname: %d\n", + __func__, rc); + } mutex_unlock(&server->srv_mutex); msleep(3000); } else { -- 2.39.2