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authorPaulo Alcantara <paulo@paulo.ac>2018-11-20 15:16:36 -0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-02-06 17:27:45 +0100
commitc3ffc8df0734aa6448ac08d288c1f7945ecc62d7 (patch)
treef56436c40daee4b6ff383798a0be6a6bacfeb83c
parentf6db72280410d25b54a3067803231ede93c863a2 (diff)
cifs: Always resolve hostname before reconnecting
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 <stfrench@microsoft.com> Signed-off-by: Paulo Alcantara <palcantara@suse.de> Signed-off-by: Steve French <stfrench@microsoft.com> Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/cifs/connect.c53
1 files changed, 53 insertions, 0 deletions
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index b83ab72cf855..b14e1abb891c 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -50,6 +50,7 @@
#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"
@@ -319,6 +320,53 @@ static int cifs_setup_volume_info(struct smb_vol *volume_info, char *mount_data,
const char *devname, bool is_smb3);
/*
+ * 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
*
* mark tcp session as reconnecting so temporarily locked
@@ -418,6 +466,11 @@ 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 {