cifs: do not depend on release_iface for maintaining iface_list

commit 09eeb0723f219fbd96d8865bf9b935e03ee2ec22 upstream.

parse_server_interfaces should be in complete charge of maintaining
the iface_list linked list. Today, iface entries are removed
from the list only when the last refcount is dropped.
i.e. in release_iface. However, this can result in undercounting
of refcount if the server stops advertising interfaces (which
Azure SMB server does).

This change puts parse_server_interfaces in full charge of
maintaining the iface_list. So if an empty list is returned
by the server, the entries in the list will immediately be
removed. This way, a following call to the same function will
not find entries in the list.

Fixes: aa45dadd34e4 ("cifs: change iface_list from array to sorted linked list")
Cc: stable@vger.kernel.org
Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 4eac7dc..ec1e5e2 100644 (file)
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -993,7 +993,6 @@ release_iface(struct kref *ref)
        struct cifs_server_iface *iface = container_of(ref,
                                                       struct cifs_server_iface,
                                                       refcount);
-       list_del_init(&iface->iface_head);
        kfree(iface);
 }
 

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 90a881b..94e4af4 100644 (file)
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -593,16 +593,12 @@ parse_server_interfaces(struct network_interface_info_ioctl_rsp *buf,
        }
 
        /*
-        * Go through iface_list and do kref_put to remove
-        * any unused ifaces. ifaces in use will be removed
-        * when the last user calls a kref_put on it
+        * Go through iface_list and mark them as inactive
         */
        list_for_each_entry_safe(iface, niface, &ses->iface_list,
-                                iface_head) {
+                                iface_head)
                iface->is_active = 0;
-               kref_put(&iface->refcount, release_iface);
-               ses->iface_count--;
-       }
+
        spin_unlock(&ses->iface_lock);
 
        /*
@@ -676,10 +672,7 @@ parse_server_interfaces(struct network_interface_info_ioctl_rsp *buf,
                                         iface_head) {
                        ret = iface_cmp(iface, &tmp_iface);
                        if (!ret) {
-                               /* just get a ref so that it doesn't get picked/freed */
                                iface->is_active = 1;
-                               kref_get(&iface->refcount);
-                               ses->iface_count++;
                                spin_unlock(&ses->iface_lock);
                                goto next_iface;
                        } else if (ret < 0) {
@@ -746,6 +739,20 @@ next_iface:
        }
 
 out:
+       /*
+        * Go through the list again and put the inactive entries
+        */
+       spin_lock(&ses->iface_lock);
+       list_for_each_entry_safe(iface, niface, &ses->iface_list,
+                                iface_head) {
+               if (!iface->is_active) {
+                       list_del(&iface->iface_head);
+                       kref_put(&iface->refcount, release_iface);
+                       ses->iface_count--;
+               }
+       }
+       spin_unlock(&ses->iface_lock);
+
        return rc;
 }